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受欢迎的三角函数 >

tan(x-45)-tan(x+45)=4

解答

tan (x - 4 5^{\circ}) - tan (x + 4 5^{\circ}) = 4

解答

x = 12 0^{\circ} + 18 0^{\circ} n, x = 6 0^{\circ} + 18 0^{\circ} n

+1

弧度

x = \frac{2 π}{3} + πn, x = \frac{π}{3} + πn

求解步骤

tan (x - 4 5^{\circ}) - tan (x + 4 5^{\circ}) = 4

使用三角恒等式改写

tan (x - 4 5^{\circ}) - tan (x + 4 5^{\circ}) = 4

使用三角恒等式改写

tan (x - 4 5^{\circ})

使用基本三角恒等式:

tan (x) = \frac{sin ( x )}{cos ( x )}

= \frac{sin ( x - 4 5 ^{\circ} )}{cos ( x - 4 5 ^{\circ} )}

使用角差恒等式:

sin (s - t) = sin (s) cos (t) - cos (s) sin (t)

= \frac{sin ( x ) cos ( 4 5 ^{\circ} ) - cos ( x ) sin ( 4 5 ^{\circ} )}{cos ( x - 4 5 ^{\circ} )}

使用角差恒等式:

cos (s - t) = cos (s) cos (t) + sin (s) sin (t)

= \frac{sin ( x ) cos ( 4 5 ^{\circ} ) - cos ( x ) sin ( 4 5 ^{\circ} )}{cos ( x ) cos ( 4 5 ^{\circ} ) + sin ( x ) sin ( 4 5 ^{\circ} )}

化简

\frac{sin ( x ) cos ( 4 5 ^{\circ} ) - cos ( x ) sin ( 4 5 ^{\circ} )}{cos ( x ) cos ( 4 5 ^{\circ} ) + sin ( x ) sin ( 4 5 ^{\circ} )} : \frac{sin ( x ) - cos ( x )}{cos ( x ) + sin ( x )}

\frac{sin ( x ) cos ( 4 5 ^{\circ} ) - cos ( x ) sin ( 4 5 ^{\circ} )}{cos ( x ) cos ( 4 5 ^{\circ} ) + sin ( x ) sin ( 4 5 ^{\circ} )}

sin (x) cos (4 5^{\circ}) - cos (x) sin (4 5^{\circ}) = \frac{2}{2} sin (x) - \frac{2}{2} cos (x)

sin (x) cos (4 5^{\circ}) - cos (x) sin (4 5^{\circ})

化简

cos (4 5^{\circ}) : \frac{2}{2}

cos (4 5^{\circ})

使用以下普通恒等式:

cos (4 5^{\circ}) = \frac{2}{2}

cos (x)

周期表（周期为

36 0^{\circ} n

）：

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= \frac{2}{2}

= \frac{2}{2} sin (x) - sin (4 5^{\circ}) cos (x)

化简

sin (4 5^{\circ}) : \frac{2}{2}

sin (4 5^{\circ})

使用以下普通恒等式:

sin (4 5^{\circ}) = \frac{2}{2}

sin (x)

周期表（周期为

36 0^{\circ} n

"）：

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

= \frac{2}{2}

= \frac{2}{2} sin (x) - \frac{2}{2} cos (x)

= \frac{\frac{2}{2} sin ( x ) - \frac{2}{2} cos ( x )}{cos ( 4 5 ^{\circ} ) cos ( x ) + sin ( 4 5 ^{\circ} ) sin ( x )}

cos (x) cos (4 5^{\circ}) + sin (x) sin (4 5^{\circ}) = \frac{2}{2} cos (x) + \frac{2}{2} sin (x)

cos (x) cos (4 5^{\circ}) + sin (x) sin (4 5^{\circ})

化简

cos (4 5^{\circ}) : \frac{2}{2}

cos (4 5^{\circ})

使用以下普通恒等式:

cos (4 5^{\circ}) = \frac{2}{2}

cos (x)

周期表（周期为

36 0^{\circ} n

）：

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= \frac{2}{2}

= \frac{2}{2} cos (x) + sin (4 5^{\circ}) sin (x)

化简

sin (4 5^{\circ}) : \frac{2}{2}

sin (4 5^{\circ})

使用以下普通恒等式:

sin (4 5^{\circ}) = \frac{2}{2}

sin (x)

周期表（周期为

36 0^{\circ} n

"）：

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

= \frac{2}{2}

= \frac{2}{2} cos (x) + \frac{2}{2} sin (x)

= \frac{\frac{2}{2} sin ( x ) - \frac{2}{2} cos ( x )}{\frac{2}{2} cos ( x ) + \frac{2}{2} sin ( x )}

乘

cos (x) \frac{2}{2} : \frac{2 cos ( x )}{2}

cos (x) \frac{2}{2}

分式相乘:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{2 cos ( x )}{2}

= \frac{\frac{2}{2} sin ( x ) - \frac{2}{2} cos ( x )}{\frac{2 c o s ( x )}{2} + \frac{2}{2} sin ( x )}

乘

sin (x) \frac{2}{2} : \frac{2 sin ( x )}{2}

sin (x) \frac{2}{2}

分式相乘:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{2 sin ( x )}{2}

= \frac{\frac{2}{2} sin ( x ) - \frac{2}{2} cos ( x )}{\frac{2 c o s ( x )}{2} + \frac{2 s i n ( x )}{2}}

乘

sin (x) \frac{2}{2} : \frac{2 sin ( x )}{2}

sin (x) \frac{2}{2}

分式相乘:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{2 sin ( x )}{2}

= \frac{\frac{2 s i n ( x )}{2} - \frac{2}{2} cos ( x )}{\frac{2 c o s ( x )}{2} + \frac{2 s i n ( x )}{2}}

乘

cos (x) \frac{2}{2} : \frac{2 cos ( x )}{2}

cos (x) \frac{2}{2}

分式相乘:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{2 cos ( x )}{2}

= \frac{\frac{2 s i n ( x )}{2} - \frac{2 c o s ( x )}{2}}{\frac{2 c o s ( x )}{2} + \frac{2 s i n ( x )}{2}}

合并分式

\frac{2 cos ( x )}{2} + \frac{2 sin ( x )}{2} : \frac{2 cos ( x ) + 2 sin ( x )}{2}

使用法则

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{2 cos ( x ) + 2 sin ( x )}{2}

= \frac{\frac{2 s i n ( x )}{2} - \frac{2 c o s ( x )}{2}}{\frac{2 c o s ( x ) + 2 s i n ( x )}{2}}

合并分式

\frac{2 sin ( x )}{2} - \frac{2 cos ( x )}{2} : \frac{2 sin ( x ) - 2 cos ( x )}{2}

使用法则

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{2 sin ( x ) - 2 cos ( x )}{2}

= \frac{\frac{2 s i n ( x ) - 2 c o s ( x )}{2}}{\frac{2 c o s ( x ) + 2 s i n ( x )}{2}}

分式相除:

\frac{\frac{a}{b}}{\frac{c}{d}} = \frac{a \cdot d}{b \cdot c}

= \frac{( 2 sin ( x ) - 2 cos ( x ) ) \cdot 2}{2 ( 2 cos ( x ) + 2 sin ( x ) )}

约分:

2

= \frac{2 sin ( x ) - 2 cos ( x )}{2 cos ( x ) + 2 sin ( x )}

因式分解出通项

2

= \frac{2 ( sin ( x ) - cos ( x ) )}{2 cos ( x ) + 2 sin ( x )}

因式分解出通项

2

= \frac{2 ( sin ( x ) - cos ( x ) )}{2 ( cos ( x ) + sin ( x ) )}

约分:

2

= \frac{sin ( x ) - cos ( x )}{cos ( x ) + sin ( x )}

= \frac{sin ( x ) - cos ( x )}{cos ( x ) + sin ( x )}

使用基本三角恒等式:

tan (x) = \frac{sin ( x )}{cos ( x )}

= \frac{sin ( x + 4 5 ^{\circ} )}{cos ( x + 4 5 ^{\circ} )}

使用角和恒等式:

sin (s + t) = sin (s) cos (t) + cos (s) sin (t)

= \frac{sin ( x ) cos ( 4 5 ^{\circ} ) + cos ( x ) sin ( 4 5 ^{\circ} )}{cos ( x + 4 5 ^{\circ} )}

使用角和恒等式:

cos (s + t) = cos (s) cos (t) - sin (s) sin (t)

= \frac{sin ( x ) cos ( 4 5 ^{\circ} ) + cos ( x ) sin ( 4 5 ^{\circ} )}{cos ( x ) cos ( 4 5 ^{\circ} ) - sin ( x ) sin ( 4 5 ^{\circ} )}

化简

\frac{sin ( x ) cos ( 4 5 ^{\circ} ) + cos ( x ) sin ( 4 5 ^{\circ} )}{cos ( x ) cos ( 4 5 ^{\circ} ) - sin ( x ) sin ( 4 5 ^{\circ} )} : \frac{sin ( x ) + cos ( x )}{cos ( x ) - sin ( x )}

\frac{sin ( x ) cos ( 4 5 ^{\circ} ) + cos ( x ) sin ( 4 5 ^{\circ} )}{cos ( x ) cos ( 4 5 ^{\circ} ) - sin ( x ) sin ( 4 5 ^{\circ} )}

sin (x) cos (4 5^{\circ}) + cos (x) sin (4 5^{\circ}) = \frac{2}{2} sin (x) + \frac{2}{2} cos (x)

sin (x) cos (4 5^{\circ}) + cos (x) sin (4 5^{\circ})

化简

cos (4 5^{\circ}) : \frac{2}{2}

cos (4 5^{\circ})

使用以下普通恒等式:

cos (4 5^{\circ}) = \frac{2}{2}

cos (x)

周期表（周期为

36 0^{\circ} n

）：

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= \frac{2}{2}

= \frac{2}{2} sin (x) + sin (4 5^{\circ}) cos (x)

化简

sin (4 5^{\circ}) : \frac{2}{2}

sin (4 5^{\circ})

使用以下普通恒等式:

sin (4 5^{\circ}) = \frac{2}{2}

sin (x)

周期表（周期为

36 0^{\circ} n

"）：

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

= \frac{2}{2}

= \frac{2}{2} sin (x) + \frac{2}{2} cos (x)

= \frac{\frac{2}{2} sin ( x ) + \frac{2}{2} cos ( x )}{cos ( 4 5 ^{\circ} ) cos ( x ) - sin ( 4 5 ^{\circ} ) sin ( x )}

cos (x) cos (4 5^{\circ}) - sin (x) sin (4 5^{\circ}) = \frac{2}{2} cos (x) - \frac{2}{2} sin (x)

cos (x) cos (4 5^{\circ}) - sin (x) sin (4 5^{\circ})

化简

cos (4 5^{\circ}) : \frac{2}{2}

cos (4 5^{\circ})

使用以下普通恒等式:

cos (4 5^{\circ}) = \frac{2}{2}

cos (x)

周期表（周期为

36 0^{\circ} n

）：

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= \frac{2}{2}

= \frac{2}{2} cos (x) - sin (4 5^{\circ}) sin (x)

化简

sin (4 5^{\circ}) : \frac{2}{2}

sin (4 5^{\circ})

使用以下普通恒等式:

sin (4 5^{\circ}) = \frac{2}{2}

sin (x)

周期表（周期为

36 0^{\circ} n

"）：

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

= \frac{2}{2}

= \frac{2}{2} cos (x) - \frac{2}{2} sin (x)

= \frac{\frac{2}{2} sin ( x ) + \frac{2}{2} cos ( x )}{\frac{2}{2} cos ( x ) - \frac{2}{2} sin ( x )}

乘

cos (x) \frac{2}{2} : \frac{2 cos ( x )}{2}

cos (x) \frac{2}{2}

分式相乘:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{2 cos ( x )}{2}

= \frac{\frac{2}{2} sin ( x ) + \frac{2}{2} cos ( x )}{\frac{2 c o s ( x )}{2} - \frac{2}{2} sin ( x )}

乘

sin (x) \frac{2}{2} : \frac{2 sin ( x )}{2}

sin (x) \frac{2}{2}

分式相乘:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{2 sin ( x )}{2}

= \frac{\frac{2}{2} sin ( x ) + \frac{2}{2} cos ( x )}{\frac{2 c o s ( x )}{2} - \frac{2 s i n ( x )}{2}}

乘

sin (x) \frac{2}{2} : \frac{2 sin ( x )}{2}

sin (x) \frac{2}{2}

分式相乘:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{2 sin ( x )}{2}

= \frac{\frac{2 s i n ( x )}{2} + \frac{2}{2} cos ( x )}{\frac{2 c o s ( x )}{2} - \frac{2 s i n ( x )}{2}}

乘

cos (x) \frac{2}{2} : \frac{2 cos ( x )}{2}

cos (x) \frac{2}{2}

分式相乘:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{2 cos ( x )}{2}

= \frac{\frac{2 s i n ( x )}{2} + \frac{2 c o s ( x )}{2}}{\frac{2 c o s ( x )}{2} - \frac{2 s i n ( x )}{2}}

合并分式

\frac{2 cos ( x )}{2} - \frac{2 sin ( x )}{2} : \frac{2 cos ( x ) - 2 sin ( x )}{2}

使用法则

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{2 cos ( x ) - 2 sin ( x )}{2}

= \frac{\frac{2 s i n ( x )}{2} + \frac{2 c o s ( x )}{2}}{\frac{2 c o s ( x ) - 2 s i n ( x )}{2}}

合并分式

\frac{2 sin ( x )}{2} + \frac{2 cos ( x )}{2} : \frac{2 sin ( x ) + 2 cos ( x )}{2}

使用法则

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{2 sin ( x ) + 2 cos ( x )}{2}

= \frac{\frac{2 s i n ( x ) + 2 c o s ( x )}{2}}{\frac{2 c o s ( x ) - 2 s i n ( x )}{2}}

分式相除:

\frac{\frac{a}{b}}{\frac{c}{d}} = \frac{a \cdot d}{b \cdot c}

= \frac{( 2 sin ( x ) + 2 cos ( x ) ) \cdot 2}{2 ( 2 cos ( x ) - 2 sin ( x ) )}

约分:

2

= \frac{2 sin ( x ) + 2 cos ( x )}{2 cos ( x ) - 2 sin ( x )}

因式分解出通项

2

= \frac{2 ( sin ( x ) + cos ( x ) )}{2 cos ( x ) - 2 sin ( x )}

因式分解出通项

2

= \frac{2 ( sin ( x ) + cos ( x ) )}{2 ( cos ( x ) - sin ( x ) )}

约分:

2

= \frac{sin ( x ) + cos ( x )}{cos ( x ) - sin ( x )}

= \frac{sin ( x ) + cos ( x )}{cos ( x ) - sin ( x )}

\frac{sin ( x ) - cos ( x )}{cos ( x ) + sin ( x )} - \frac{sin ( x ) + cos ( x )}{cos ( x ) - sin ( x )} = 4

化简

\frac{sin ( x ) - cos ( x )}{cos ( x ) + sin ( x )} - \frac{sin ( x ) + cos ( x )}{cos ( x ) - sin ( x )} : \frac{- 2 sin ^{2} ( x ) - 2 cos ^{2} ( x )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )}

\frac{sin ( x ) - cos ( x )}{cos ( x ) + sin ( x )} - \frac{sin ( x ) + cos ( x )}{cos ( x ) - sin ( x )}

cos (x) + sin (x), cos (x) - sin (x)

的最小公倍数:

(cos (x) + sin (x)) (cos (x) - sin (x))

cos (x) + sin (x), cos (x) - sin (x)

最小公倍数 (LCM)

计算出由出现在

cos (x) + sin (x)

或

cos (x) - sin (x)

中的因子组成的表达式

= (cos (x) + sin (x)) (cos (x) - sin (x))

根据最小公倍数调整分式

将每个分子乘以其分母转变为最小公倍数所要乘以的同一数值

(cos (x) + sin (x)) (cos (x) - sin (x))

对于

\frac{sin ( x ) - cos ( x )}{cos ( x ) + sin ( x )} :

将分母和分子乘以

cos (x) - sin (x)

\frac{sin ( x ) - cos ( x )}{cos ( x ) + sin ( x )} = \frac{( sin ( x ) - cos ( x ) ) ( cos ( x ) - sin ( x ) )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )}

对于

\frac{sin ( x ) + cos ( x )}{cos ( x ) - sin ( x )} :

将分母和分子乘以

cos (x) + sin (x)

\frac{sin ( x ) + cos ( x )}{cos ( x ) - sin ( x )} = \frac{( sin ( x ) + cos ( x ) ) ( cos ( x ) + sin ( x ) )}{( cos ( x ) - sin ( x ) ) ( cos ( x ) + sin ( x ) )} = \frac{( sin ( x ) + cos ( x ) ) ^{2}}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )}

= \frac{( sin ( x ) - cos ( x ) ) ( cos ( x ) - sin ( x ) )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )} - \frac{( sin ( x ) + cos ( x ) ) ^{2}}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )}

因为分母相等，所以合并分式:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{( sin ( x ) - cos ( x ) ) ( cos ( x ) - sin ( x ) ) - ( sin ( x ) + cos ( x ) ) ^{2}}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )}

乘开

(sin (x) - cos (x)) (cos (x) - sin (x)) - (sin (x) + cos (x))^{2} : - 2 sin^{2} (x) - 2 cos^{2} (x)

(sin (x) - cos (x)) (cos (x) - sin (x)) - (sin (x) + cos (x))^{2}

(sin (x) + cos (x))^{2} : sin^{2} (x) + 2 sin (x) cos (x) + cos^{2} (x)

使用完全平方公式:

(a + b)^{2} = a^{2} + 2 ab + b^{2}

a = sin (x), b = cos (x)

= sin^{2} (x) + 2 sin (x) cos (x) + cos^{2} (x)

= (sin (x) - cos (x)) (cos (x) - sin (x)) - (sin^{2} (x) + 2 sin (x) cos (x) + cos^{2} (x))

乘开

(sin (x) - cos (x)) (cos (x) - sin (x)) : 2 cos (x) sin (x) - sin^{2} (x) - cos^{2} (x)

(sin (x) - cos (x)) (cos (x) - sin (x))

使用 FOIL 方法:

(a + b) (c + d) = a c + a d + b c + b d

a = sin (x), b = - cos (x), c = cos (x), d = - sin (x)

= sin (x) cos (x) + sin (x) (- sin (x)) + (- cos (x)) cos (x) + (- cos (x)) (- sin (x))

使用加减运算法则

+ (- a) = - a, (- a) (- b) = ab

= sin (x) cos (x) - sin (x) sin (x) - cos (x) cos (x) + cos (x) sin (x)

化简

sin (x) cos (x) - sin (x) sin (x) - cos (x) cos (x) + cos (x) sin (x) : 2 cos (x) sin (x) - sin^{2} (x) - cos^{2} (x)

sin (x) cos (x) - sin (x) sin (x) - cos (x) cos (x) + cos (x) sin (x)

同类项相加:

sin (x) cos (x) + cos (x) sin (x) = 2 cos (x) sin (x)

= 2 cos (x) sin (x) - sin (x) sin (x) - cos (x) cos (x)

sin (x) sin (x) = sin^{2} (x)

sin (x) sin (x)

使用指数法则:

a^{b} \cdot a^{c} = a^{b + c}

sin (x) sin (x) = sin^{1 + 1} (x)

= sin^{1 + 1} (x)

数字相加:

1 + 1 = 2

= sin^{2} (x)

cos (x) cos (x) = cos^{2} (x)

cos (x) cos (x)

使用指数法则:

a^{b} \cdot a^{c} = a^{b + c}

cos (x) cos (x) = cos^{1 + 1} (x)

= cos^{1 + 1} (x)

数字相加:

1 + 1 = 2

= cos^{2} (x)

= 2 cos (x) sin (x) - sin^{2} (x) - cos^{2} (x)

= 2 cos (x) sin (x) - sin^{2} (x) - cos^{2} (x)

= 2 cos (x) sin (x) - sin^{2} (x) - cos^{2} (x) - (sin^{2} (x) + 2 sin (x) cos (x) + cos^{2} (x))

- (sin^{2} (x) + 2 sin (x) cos (x) + cos^{2} (x)) : - sin^{2} (x) - 2 sin (x) cos (x) - cos^{2} (x)

- (sin^{2} (x) + 2 sin (x) cos (x) + cos^{2} (x))

打开括号

= - (sin^{2} (x)) - (2 sin (x) cos (x)) - (cos^{2} (x))

使用加减运算法则

+ (- a) = - a

= - sin^{2} (x) - 2 sin (x) cos (x) - cos^{2} (x)

= 2 cos (x) sin (x) - sin^{2} (x) - cos^{2} (x) - sin^{2} (x) - 2 sin (x) cos (x) - cos^{2} (x)

化简

2 cos (x) sin (x) - sin^{2} (x) - cos^{2} (x) - sin^{2} (x) - 2 sin (x) cos (x) - cos^{2} (x) : - 2 sin^{2} (x) - 2 cos^{2} (x)

2 cos (x) sin (x) - sin^{2} (x) - cos^{2} (x) - sin^{2} (x) - 2 sin (x) cos (x) - cos^{2} (x)

同类项相加:

2 cos (x) sin (x) - 2 sin (x) cos (x) = 0

= - sin^{2} (x) - cos^{2} (x) - sin^{2} (x) - cos^{2} (x)

同类项相加:

- cos^{2} (x) - cos^{2} (x) = - 2 cos^{2} (x)

= - sin^{2} (x) - 2 cos^{2} (x) - sin^{2} (x)

同类项相加:

- sin^{2} (x) - sin^{2} (x) = - 2 sin^{2} (x)

= - 2 sin^{2} (x) - 2 cos^{2} (x)

= - 2 sin^{2} (x) - 2 cos^{2} (x)

= \frac{- 2 sin ^{2} ( x ) - 2 cos ^{2} ( x )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )}

\frac{- 2 sin ^{2} ( x ) - 2 cos ^{2} ( x )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )} = 4

\frac{- 2 sin ^{2} ( x ) - 2 cos ^{2} ( x )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )} = 4

两边减去

4

\frac{- 2 sin ^{2} ( x ) - 2 cos ^{2} ( x )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )} - 4 = 0

化简

\frac{- 2 sin ^{2} ( x ) - 2 cos ^{2} ( x )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )} - 4 : \frac{2 sin ^{2} ( x ) - 6 cos ^{2} ( x )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )}

\frac{- 2 sin ^{2} ( x ) - 2 cos ^{2} ( x )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )} - 4

将项转换为分式:

4 = \frac{4 ( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )}

= \frac{- 2 sin ^{2} ( x ) - 2 cos ^{2} ( x )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )} - \frac{4 ( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )}

因为分母相等，所以合并分式:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{- 2 sin ^{2} ( x ) - 2 cos ^{2} ( x ) - 4 ( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )}

乘开

- 2 sin^{2} (x) - 2 cos^{2} (x) - 4 (cos (x) + sin (x)) (cos (x) - sin (x)) : 2 sin^{2} (x) - 6 cos^{2} (x)

- 2 sin^{2} (x) - 2 cos^{2} (x) - 4 (cos (x) + sin (x)) (cos (x) - sin (x))

乘开

- 4 (cos (x) + sin (x)) (cos (x) - sin (x)) : - 4 cos^{2} (x) + 4 sin^{2} (x)

乘开

(cos (x) + sin (x)) (cos (x) - sin (x)) : cos^{2} (x) - sin^{2} (x)

(cos (x) + sin (x)) (cos (x) - sin (x))

使用平方差公式:

(a + b) (a - b) = a^{2} - b^{2}

a = cos (x), b = sin (x)

= cos^{2} (x) - sin^{2} (x)

= - 4 (cos^{2} (x) - sin^{2} (x))

乘开

- 4 (cos^{2} (x) - sin^{2} (x)) : - 4 cos^{2} (x) + 4 sin^{2} (x)

- 4 (cos^{2} (x) - sin^{2} (x))

使用分配律:

a (b - c) = ab - a c

a = - 4, b = cos^{2} (x), c = sin^{2} (x)

= - 4 cos^{2} (x) - (- 4) sin^{2} (x)

使用加减运算法则

- (- a) = a

= - 4 cos^{2} (x) + 4 sin^{2} (x)

= - 4 cos^{2} (x) + 4 sin^{2} (x)

= - 2 sin^{2} (x) - 2 cos^{2} (x) - 4 cos^{2} (x) + 4 sin^{2} (x)

化简

- 2 sin^{2} (x) - 2 cos^{2} (x) - 4 cos^{2} (x) + 4 sin^{2} (x) : 2 sin^{2} (x) - 6 cos^{2} (x)

- 2 sin^{2} (x) - 2 cos^{2} (x) - 4 cos^{2} (x) + 4 sin^{2} (x)

同类项相加:

- 2 cos^{2} (x) - 4 cos^{2} (x) = - 6 cos^{2} (x)

= - 2 sin^{2} (x) - 6 cos^{2} (x) + 4 sin^{2} (x)

同类项相加:

- 2 sin^{2} (x) + 4 sin^{2} (x) = 2 sin^{2} (x)

= 2 sin^{2} (x) - 6 cos^{2} (x)

= 2 sin^{2} (x) - 6 cos^{2} (x)

= \frac{2 sin ^{2} ( x ) - 6 cos ^{2} ( x )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )}

\frac{2 sin ^{2} ( x ) - 6 cos ^{2} ( x )}{( cos ( x ) + sin ( x ) ) ( cos ( x ) - sin ( x ) )} = 0

\frac{f ( x )}{g ( x )} = 0 \Rightarrow f (x) = 0

2 sin^{2} (x) - 6 cos^{2} (x) = 0

分解

2 sin^{2} (x) - 6 cos^{2} (x) : 2 (sin (x) + 3 cos (x)) (sin (x) - 3 cos (x))

2 sin^{2} (x) - 6 cos^{2} (x)

将

- 6

改写为

3 \cdot 2

= 2 sin^{2} (x) + 3 \cdot 2 cos^{2} (x)

因式分解出通项

2

= 2 (sin^{2} (x) - 3 cos^{2} (x))

分解

sin^{2} (x) - 3 cos^{2} (x) : (sin (x) + 3 cos (x)) (sin (x) - 3 cos (x))

sin^{2} (x) - 3 cos^{2} (x)

将

sin^{2} (x) - 3 cos^{2} (x)

改写为

sin^{2} (x) - (3 cos (x))^{2}

sin^{2} (x) - 3 cos^{2} (x)

使用根式运算法则:

a = (a)^{2}

3 = (3)^{2}

= sin^{2} (x) - (3)^{2} cos^{2} (x)

使用指数法则:

a^{m} b^{m} = (ab)^{m}

(3)^{2} cos^{2} (x) = (3 cos (x))^{2}

= sin^{2} (x) - (3 cos (x))^{2}

= sin^{2} (x) - (3 cos (x))^{2}

使用平方差公式:

x^{2} - y^{2} = (x + y) (x - y)

sin^{2} (x) - (3 cos (x))^{2} = (sin (x) + 3 cos (x)) (sin (x) - 3 cos (x))

= (sin (x) + 3 cos (x)) (sin (x) - 3 cos (x))

= 2 (sin (x) + 3 cos (x)) (sin (x) - 3 cos (x))

2 (sin (x) + 3 cos (x)) (sin (x) - 3 cos (x)) = 0

分别求解每个部分

sin (x) + 3 cos (x) = 0 or sin (x) - 3 cos (x) = 0

sin (x) + 3 cos (x) = 0 : x = 12 0^{\circ} + 18 0^{\circ} n

sin (x) + 3 cos (x) = 0

使用三角恒等式改写

sin (x) + 3 cos (x) = 0

在两边除以

cos (x), cos (x) \neq = 0

\frac{sin ( x ) + 3 cos ( x )}{cos ( x )} = \frac{0}{cos ( x )}

化简

\frac{sin ( x )}{cos ( x )} + 3 = 0

使用基本三角恒等式:

\frac{sin ( x )}{cos ( x )} = tan (x)

tan (x) + 3 = 0

tan (x) + 3 = 0

将

3

到右边

tan (x) + 3 = 0

两边减去

3

tan (x) + 3 - 3 = 0 - 3

化简

tan (x) = - 3

tan (x) = - 3

tan (x) = - 3

的通解

tan (x)

周期表（周期为

18 0^{\circ} n

）：

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} tan (x) 0 \frac{3}{3} 13 \pm \infty - 3 - 1 - \frac{3}{3}

x = 12 0^{\circ} + 18 0^{\circ} n

x = 12 0^{\circ} + 18 0^{\circ} n

sin (x) - 3 cos (x) = 0 : x = 6 0^{\circ} + 18 0^{\circ} n

sin (x) - 3 cos (x) = 0

使用三角恒等式改写

sin (x) - 3 cos (x) = 0

在两边除以

cos (x), cos (x) \neq = 0

\frac{sin ( x ) - 3 cos ( x )}{cos ( x )} = \frac{0}{cos ( x )}

化简

\frac{sin ( x )}{cos ( x )} - 3 = 0

使用基本三角恒等式:

\frac{sin ( x )}{cos ( x )} = tan (x)

tan (x) - 3 = 0

tan (x) - 3 = 0

将

3

到右边

tan (x) - 3 = 0

两边加上

3

tan (x) - 3 + 3 = 0 + 3

化简

tan (x) = 3

tan (x) = 3

tan (x) = 3

的通解

tan (x)

周期表（周期为

18 0^{\circ} n

）：

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} tan (x) 0 \frac{3}{3} 13 \pm \infty - 3 - 1 - \frac{3}{3}

x = 6 0^{\circ} + 18 0^{\circ} n

x = 6 0^{\circ} + 18 0^{\circ} n

合并所有解

x = 12 0^{\circ} + 18 0^{\circ} n, x = 6 0^{\circ} + 18 0^{\circ} n

作图

流行的例子

sin(2x)=10cos(x)

sin (2 x) = 10 cos (x)

3-4sin(θ)=4-6sin(θ)

3 - 4 sin (θ) = 4 - 6 sin (θ)

tan (x) = - 1.036

tan (2 x) = \frac{24}{7}

solvefor x,80=75-60cos(([pi*x])/(15))

so l v e f or x, 80 = 75 - 60 cos (\frac{[ π \cdot x ]}{15})