zs

English

Español

Português

Français

Deutsch

Italiano

Русский

中文(简体)

한국어

日本語

Tiếng Việt

עברית

العربية

受欢迎的三角函数 >

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

解答

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

解答

x = 2 πn, x = π + 2 πn

+1

度数

x = 0^{\circ} + 36 0^{\circ} n, x = 18 0^{\circ} + 36 0^{\circ} n

求解步骤

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

两边减去

\frac{1 - cos ^{2} ( x )}{2}

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

化简

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

sin^{2} (x) - \frac{1 - cos ^{2} ( x )}{2}

将项转换为分式:

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

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

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 ^{2} ( x ) \cdot 2 - ( 1 - cos ^{2} ( x ) )}{2}

乘开

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

sin^{2} (x) \cdot 2 - (1 - cos^{2} (x))

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

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

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

打开括号

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

使用加减运算法则

- (- a) = a, - (a) = - a

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

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

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

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

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

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

使用三角恒等式改写

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

使用毕达哥拉斯恒等式:

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

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

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

化简

= sin^{2} (x)

sin^{2} (x) = 0

使用法则

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

sin (x) = 0

sin (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}

x = 0 + 2 πn, x = π + 2 πn

x = 0 + 2 πn, x = π + 2 πn

解

x = 0 + 2 πn : x = 2 πn

x = 0 + 2 πn

0 + 2 πn = 2 πn

x = 2 πn

x = 2 πn, x = π + 2 πn

作图

流行的例子

cot(θ)=cos(θ)

cot (θ) = cos (θ)

3csc^3(x)-4csc(x)=0

3 csc^{3} (x) - 4 csc (x) = 0

tan(θ)=(6.06)/(-33.5)

tan (θ) = \frac{6.06}{- 33.5}

csc(θ)=(sqrt(13))/2 ,sec(θ)=(sqrt(13))/3

csc (θ) = \frac{13}{2}, sec (θ) = \frac{13}{3}

4cos^2(x)+cos(2x)-7cos(x)=-2,0<= x<= 360

4 cos^{2} (x) + cos (2 x) - 7 cos (x) = - 2, 0^{\circ} \leq x \leq 36 0^{\circ}