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受欢迎的三角函数 >

cos(3x-pi/4)= 1/(sqrt(2)),0<= x<= pi

解答

cos (3 x - \frac{π}{4}) = \frac{1}{2}, 0 \leq x \leq π

解答

x = \frac{π}{6}, x = \frac{2 π}{3}, x = \frac{5 π}{6}, x = 0

求解步骤

cos (3 x - \frac{π}{4}) = \frac{1}{2}, 0 \leq x \leq π

化简

\frac{1}{2} : \frac{2}{2}

\frac{1}{2}

乘以共轭根式

\frac{2}{2}

= \frac{1 \cdot 2}{2 2}

1 \cdot 2 = 2

22 = 2

22

使用根式运算法则:

a a = a

22 = 2

= 2

= \frac{2}{2}

cos (3 x - \frac{π}{4}) = \frac{2}{2}

cos (3 x - \frac{π}{4}) = \frac{2}{2}

的通解

cos (x)

周期表（周期为

2 πn

）：

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

3 x - \frac{π}{4} = \frac{π}{4} + 2 πn, 3 x - \frac{π}{4} = \frac{7 π}{4} + 2 πn

3 x - \frac{π}{4} = \frac{π}{4} + 2 πn, 3 x - \frac{π}{4} = \frac{7 π}{4} + 2 πn

解

3 x - \frac{π}{4} = \frac{π}{4} + 2 πn : x = \frac{π}{6} + \frac{2 πn}{3}

3 x - \frac{π}{4} = \frac{π}{4} + 2 πn

将

\frac{π}{4}

到右边

3 x - \frac{π}{4} = \frac{π}{4} + 2 πn

两边加上

\frac{π}{4}

3 x - \frac{π}{4} + \frac{π}{4} = \frac{π}{4} + 2 πn + \frac{π}{4}

化简

3 x - \frac{π}{4} + \frac{π}{4} = \frac{π}{4} + 2 πn + \frac{π}{4}

化简

3 x - \frac{π}{4} + \frac{π}{4} : 3 x

3 x - \frac{π}{4} + \frac{π}{4}

同类项相加:

- \frac{π}{4} + \frac{π}{4} = 0

= 3 x

化简

\frac{π}{4} + 2 πn + \frac{π}{4} : \frac{π}{2} + 2 πn

\frac{π}{4} + 2 πn + \frac{π}{4}

对同类项分组

= \frac{π}{4} + \frac{π}{4} + 2 πn

合并分式

\frac{π}{4} + \frac{π}{4} : \frac{π}{2}

使用法则

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

= \frac{π + π}{4}

同类项相加:

π + π = 2 π

= \frac{2 π}{4}

约分:

2

= \frac{π}{2}

= \frac{π}{2} + 2 πn

3 x = \frac{π}{2} + 2 πn

3 x = \frac{π}{2} + 2 πn

3 x = \frac{π}{2} + 2 πn

两边除以

3

3 x = \frac{π}{2} + 2 πn

两边除以

3

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

化简

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

化简

\frac{3 x}{3} : x

\frac{3 x}{3}

数字相除:

\frac{3}{3} = 1

= x

化简

\frac{\frac{π}{2}}{3} + \frac{2 πn}{3} : \frac{π}{6} + \frac{2 πn}{3}

\frac{\frac{π}{2}}{3} + \frac{2 πn}{3}

\frac{\frac{π}{2}}{3} = \frac{π}{6}

\frac{\frac{π}{2}}{3}

使用分式法则:

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

= \frac{π}{2 \cdot 3}

数字相乘:

2 \cdot 3 = 6

= \frac{π}{6}

= \frac{π}{6} + \frac{2 πn}{3}

x = \frac{π}{6} + \frac{2 πn}{3}

x = \frac{π}{6} + \frac{2 πn}{3}

x = \frac{π}{6} + \frac{2 πn}{3}

解

3 x - \frac{π}{4} = \frac{7 π}{4} + 2 πn : x = \frac{2 πn}{3} + \frac{2 π}{3}

3 x - \frac{π}{4} = \frac{7 π}{4} + 2 πn

将

\frac{π}{4}

到右边

3 x - \frac{π}{4} = \frac{7 π}{4} + 2 πn

两边加上

\frac{π}{4}

3 x - \frac{π}{4} + \frac{π}{4} = \frac{7 π}{4} + 2 πn + \frac{π}{4}

化简

3 x - \frac{π}{4} + \frac{π}{4} = \frac{7 π}{4} + 2 πn + \frac{π}{4}

化简

3 x - \frac{π}{4} + \frac{π}{4} : 3 x

3 x - \frac{π}{4} + \frac{π}{4}

同类项相加:

- \frac{π}{4} + \frac{π}{4} = 0

= 3 x

化简

\frac{7 π}{4} + 2 πn + \frac{π}{4} : 2 πn + 2 π

\frac{7 π}{4} + 2 πn + \frac{π}{4}

对同类项分组

= 2 πn + \frac{π}{4} + \frac{7 π}{4}

合并分式

\frac{π}{4} + \frac{7 π}{4} : 2 π

使用法则

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

= \frac{π + 7 π}{4}

同类项相加:

π + 7 π = 8 π

= \frac{8 π}{4}

数字相除:

\frac{8}{4} = 2

= 2 π

= 2 πn + 2 π

3 x = 2 πn + 2 π

3 x = 2 πn + 2 π

3 x = 2 πn + 2 π

两边除以

3

3 x = 2 πn + 2 π

两边除以

3

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

化简

x = \frac{2 πn}{3} + \frac{2 π}{3}

x = \frac{2 πn}{3} + \frac{2 π}{3}

x = \frac{π}{6} + \frac{2 πn}{3}, x = \frac{2 πn}{3} + \frac{2 π}{3}

在

0 \leq x \leq π

范围内的解

x = \frac{π}{6}, x = \frac{2 π}{3}, x = \frac{5 π}{6}, x = 0

作图

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