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受欢迎的三角函数 >

cos(x)sin(x)cos(x)=1-sin^2(x)

解答

cos (x) sin (x) cos (x) = 1 - sin^{2} (x)

解答

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

+1

度数

x = 9 0^{\circ} + 36 0^{\circ} n, x = 27 0^{\circ} + 36 0^{\circ} n

求解步骤

cos (x) sin (x) cos (x) = 1 - sin^{2} (x)

两边减去

1 - sin^{2} (x)

cos^{2} (x) sin (x) - 1 + sin^{2} (x) = 0

使用三角恒等式改写

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

使用毕达哥拉斯恒等式:

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

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

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

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

分解

- cos^{2} (x) + cos^{2} (x) sin (x) : cos^{2} (x) (sin (x) - 1)

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

因式分解出通项

cos^{2} (x)

= cos^{2} (x) (- 1 + sin (x))

cos^{2} (x) (sin (x) - 1) = 0

分别求解每个部分

cos^{2} (x) = 0 or sin (x) - 1 = 0

cos^{2} (x) = 0 : x = \frac{π}{2} + 2 πn, x = \frac{3 π}{2} + 2 πn

cos^{2} (x) = 0

使用法则

x^{n} = 0 \Rightarrow x = 0

cos (x) = 0

cos (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}

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

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

sin (x) - 1 = 0 : x = \frac{π}{2} + 2 πn

sin (x) - 1 = 0

将

1

到右边

sin (x) - 1 = 0

两边加上

1

sin (x) - 1 + 1 = 0 + 1

化简

sin (x) = 1

sin (x) = 1

sin (x) = 1

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}

x = \frac{π}{2} + 2 πn

x = \frac{π}{2} + 2 πn

合并所有解

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

作图

流行的例子

sin(θ)=sqrt(1-(1-(cos(θ)-1)^2))

14.79m=((7.61_{0}^2sin(2θ_{0}))/g)

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

sec((5θ)/4)=2,[0.2pi]

cos(x)+|cos(x)|=1,-2pi<= x<= 2pi