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受欢迎的三角函数 >

sin(7x)+sin(x)=0,0<= x<= 2pi

解答

sin (7 x) + sin (x) = 0, 0 \leq x \leq 2 π

解答

x = \frac{π}{6}, x = \frac{π}{2}, x = \frac{5 π}{6}, x = \frac{7 π}{6}, x = \frac{3 π}{2}, x = \frac{11 π}{6}, x = 0, x = \frac{π}{4}, x = \frac{3 π}{4}, x = π, x = \frac{5 π}{4}, x = \frac{7 π}{4}, x = 2 π

+1

度数

x = 3 0^{\circ}, x = 9 0^{\circ}, x = 15 0^{\circ}, x = 21 0^{\circ}, x = 27 0^{\circ}, x = 33 0^{\circ}, x = 0^{\circ}, x = 4 5^{\circ}, x = 13 5^{\circ}, x = 18 0^{\circ}, x = 22 5^{\circ}, x = 31 5^{\circ}, x = 36 0^{\circ}

求解步骤

sin (7 x) + sin (x) = 0, 0 \leq x \leq 2 π

使用三角恒等式改写

sin (7 x) + sin (x)

使用和差化积恒等式:

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

= 2 sin (\frac{7 x + x}{2}) cos (\frac{7 x - x}{2})

化简

2 sin (\frac{7 x + x}{2}) cos (\frac{7 x - x}{2}) : 2 sin (4 x) cos (3 x)

2 sin (\frac{7 x + x}{2}) cos (\frac{7 x - x}{2})

\frac{7 x + x}{2} = 4 x

\frac{7 x + x}{2}

同类项相加:

7 x + x = 8 x

= \frac{8 x}{2}

数字相除:

\frac{8}{2} = 4

= 4 x

= 2 sin (4 x) cos (\frac{7 x - x}{2})

\frac{7 x - x}{2} = 3 x

\frac{7 x - x}{2}

同类项相加:

7 x - x = 6 x

= \frac{6 x}{2}

数字相除:

\frac{6}{2} = 3

= 3 x

= 2 sin (4 x) cos (3 x)

= 2 sin (4 x) cos (3 x)

2 cos (3 x) sin (4 x) = 0

分别求解每个部分

cos (3 x) = 0 or sin (4 x) = 0

cos (3 x) = 0, 0 \leq x \leq 2 π : x = \frac{π}{6}, x = \frac{π}{2}, x = \frac{5 π}{6}, x = \frac{7 π}{6}, x = \frac{3 π}{2}, x = \frac{11 π}{6}

cos (3 x) = 0, 0 \leq x \leq 2 π

cos (3 x) = 0

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

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

解

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

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

3 x = \frac{3 π}{2} + 2 πn

两边除以

3

3 x = \frac{3 π}{2} + 2 πn

两边除以

3

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

化简

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

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

\frac{\frac{3 π}{2}}{3} = \frac{π}{2}

\frac{\frac{3 π}{2}}{3}

使用分式法则:

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

= \frac{3 π}{2 \cdot 3}

数字相乘:

2 \cdot 3 = 6

= \frac{3 π}{6}

约分:

3

= \frac{π}{2}

= \frac{π}{2} + \frac{2 πn}{3}

x = \frac{π}{2} + \frac{2 πn}{3}

x = \frac{π}{2} + \frac{2 πn}{3}

x = \frac{π}{2} + \frac{2 πn}{3}

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

在

0 \leq x \leq 2 π

范围内的解

x = \frac{π}{6}, x = \frac{π}{2}, x = \frac{5 π}{6}, x = \frac{7 π}{6}, x = \frac{3 π}{2}, x = \frac{11 π}{6}

sin (4 x) = 0, 0 \leq x \leq 2 π : x = 0, x = \frac{π}{4}, x = \frac{π}{2}, x = \frac{3 π}{4}, x = π, x = \frac{5 π}{4}, x = \frac{3 π}{2}, x = \frac{7 π}{4}, x = 2 π

sin (4 x) = 0, 0 \leq x \leq 2 π

sin (4 x) = 0

的通解

sin (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} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{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} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

4 x = 0 + 2 πn, 4 x = π + 2 πn

4 x = 0 + 2 πn, 4 x = π + 2 πn

解

4 x = 0 + 2 πn : x = \frac{πn}{2}

4 x = 0 + 2 πn

0 + 2 πn = 2 πn

4 x = 2 πn

两边除以

4

4 x = 2 πn

两边除以

4

\frac{4 x}{4} = \frac{2 πn}{4}

化简

x = \frac{πn}{2}

x = \frac{πn}{2}

解

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

4 x = π + 2 πn

两边除以

4

4 x = π + 2 πn

两边除以

4

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

化简

x = \frac{π}{4} + \frac{πn}{2}

x = \frac{π}{4} + \frac{πn}{2}

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

在

0 \leq x \leq 2 π

范围内的解

x = 0, x = \frac{π}{4}, x = \frac{π}{2}, x = \frac{3 π}{4}, x = π, x = \frac{5 π}{4}, x = \frac{3 π}{2}, x = \frac{7 π}{4}, x = 2 π

合并所有解

x = \frac{π}{6}, x = \frac{π}{2}, x = \frac{5 π}{6}, x = \frac{7 π}{6}, x = \frac{3 π}{2}, x = \frac{11 π}{6}, x = 0, x = \frac{π}{4}, x = \frac{3 π}{4}, x = π, x = \frac{5 π}{4}, x = \frac{7 π}{4}, x = 2 π

作图

流行的例子

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