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 >

9sin(x/2)+9cos(x)=0

解答

9 sin (\frac{x}{2}) + 9 cos (x) = 0

解答

x = \frac{7 π}{3} + 4 πn, x = \frac{11 π}{3} + 4 πn, x = π + 4 πn

+1

度数

x = 42 0^{\circ} + 72 0^{\circ} n, x = 66 0^{\circ} + 72 0^{\circ} n, x = 18 0^{\circ} + 72 0^{\circ} n

求解步骤

9 sin (\frac{x}{2}) + 9 cos (x) = 0

令

: u = \frac{x}{2}

9 sin (u) + 9 cos (2 u) = 0

使用三角恒等式改写

9 cos (2 u) + 9 sin (u)

使用倍角公式:

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

= 9 (1 - 2 sin^{2} (u)) + 9 sin (u)

(1 - 2 sin^{2} (u)) \cdot 9 + 9 sin (u) = 0

用替代法求解

(1 - 2 sin^{2} (u)) \cdot 9 + 9 sin (u) = 0

令

: sin (u) = u

(1 - 2 u^{2}) \cdot 9 + 9 u = 0

(1 - 2 u^{2}) \cdot 9 + 9 u = 0 : u = - \frac{1}{2}, u = 1

(1 - 2 u^{2}) \cdot 9 + 9 u = 0

展开

(1 - 2 u^{2}) \cdot 9 + 9 u : 9 - 18 u^{2} + 9 u

(1 - 2 u^{2}) \cdot 9 + 9 u

= 9 (1 - 2 u^{2}) + 9 u

乘开

9 (1 - 2 u^{2}) : 9 - 18 u^{2}

9 (1 - 2 u^{2})

使用分配律:

a (b - c) = ab - a c

a = 9, b = 1, c = 2 u^{2}

= 9 \cdot 1 - 9 \cdot 2 u^{2}

化简

9 \cdot 1 - 9 \cdot 2 u^{2} : 9 - 18 u^{2}

9 \cdot 1 - 9 \cdot 2 u^{2}

数字相乘:

9 \cdot 1 = 9

= 9 - 9 \cdot 2 u^{2}

数字相乘:

9 \cdot 2 = 18

= 9 - 18 u^{2}

= 9 - 18 u^{2}

= 9 - 18 u^{2} + 9 u

9 - 18 u^{2} + 9 u = 0

改写成标准形式

a x^{2} + b x + c = 0

- 18 u^{2} + 9 u + 9 = 0

使用求根公式求解

- 18 u^{2} + 9 u + 9 = 0

二次方程求根公式:

若

a = - 18, b = 9, c = 9

u_{1, 2} = \frac{- 9 \pm 9 ^{2} - 4 ( - 18 ) \cdot 9}{2 ( - 18 )}

u_{1, 2} = \frac{- 9 \pm 9 ^{2} - 4 ( - 18 ) \cdot 9}{2 ( - 18 )}

9^{2} - 4 (- 18) \cdot 9 = 27

9^{2} - 4 (- 18) \cdot 9

使用法则

- (- a) = a

= 9^{2} + 4 \cdot 18 \cdot 9

数字相乘:

4 \cdot 18 \cdot 9 = 648

= 9^{2} + 648

9^{2} = 81

= 81 + 648

数字相加:

81 + 648 = 729

= 729

因式分解数字:

729 = 2 7^{2}

= 2 7^{2}

使用根式运算法则:

n a^{n} = a

2 7^{2} = 27

= 27

u_{1, 2} = \frac{- 9 \pm 27}{2 ( - 18 )}

将解分隔开

u_{1} = \frac{- 9 + 27}{2 ( - 18 )}, u_{2} = \frac{- 9 - 27}{2 ( - 18 )}

u = \frac{- 9 + 27}{2 ( - 18 )} : - \frac{1}{2}

\frac{- 9 + 27}{2 ( - 18 )}

去除括号:

(- a) = - a

= \frac{- 9 + 27}{- 2 \cdot 18}

数字相加/相减:

- 9 + 27 = 18

= \frac{18}{- 2 \cdot 18}

数字相乘:

2 \cdot 18 = 36

= \frac{18}{- 36}

使用分式法则:

\frac{a}{- b} = - \frac{a}{b}

= - \frac{18}{36}

约分:

18

= - \frac{1}{2}

u = \frac{- 9 - 27}{2 ( - 18 )} : 1

\frac{- 9 - 27}{2 ( - 18 )}

去除括号:

(- a) = - a

= \frac{- 9 - 27}{- 2 \cdot 18}

数字相减:

- 9 - 27 = - 36

= \frac{- 36}{- 2 \cdot 18}

数字相乘:

2 \cdot 18 = 36

= \frac{- 36}{- 36}

使用分式法则:

\frac{- a}{- b} = \frac{a}{b}

= \frac{36}{36}

使用法则

\frac{a}{a} = 1

= 1

二次方程组的解是:

u = - \frac{1}{2}, u = 1

u = sin (u)

代回

sin (u) = - \frac{1}{2}, sin (u) = 1

sin (u) = - \frac{1}{2}, sin (u) = 1

sin (u) = - \frac{1}{2} : u = \frac{7 π}{6} + 2 πn, u = \frac{11 π}{6} + 2 πn

sin (u) = - \frac{1}{2}

sin (u) = - \frac{1}{2}

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}

u = \frac{7 π}{6} + 2 πn, u = \frac{11 π}{6} + 2 πn

u = \frac{7 π}{6} + 2 πn, u = \frac{11 π}{6} + 2 πn

sin (u) = 1 : u = \frac{π}{2} + 2 πn

sin (u) = 1

sin (u) = 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}

u = \frac{π}{2} + 2 πn

u = \frac{π}{2} + 2 πn

合并所有解

u = \frac{7 π}{6} + 2 πn, u = \frac{11 π}{6} + 2 πn, u = \frac{π}{2} + 2 πn

u = \frac{x}{2}

代回

\frac{x}{2} = \frac{7 π}{6} + 2 πn : x = \frac{7 π}{3} + 4 πn

\frac{x}{2} = \frac{7 π}{6} + 2 πn

在两边乘以

2

\frac{x}{2} = \frac{7 π}{6} + 2 πn

在两边乘以

2

\frac{2 x}{2} = 2 \cdot \frac{7 π}{6} + 2 \cdot 2 πn

化简

\frac{2 x}{2} = 2 \cdot \frac{7 π}{6} + 2 \cdot 2 πn

化简

\frac{2 x}{2} : x

\frac{2 x}{2}

数字相除:

\frac{2}{2} = 1

= x

化简

2 \cdot \frac{7 π}{6} + 2 \cdot 2 πn : \frac{7 π}{3} + 4 πn

2 \cdot \frac{7 π}{6} + 2 \cdot 2 πn

2 \cdot \frac{7 π}{6} = \frac{7 π}{3}

2 \cdot \frac{7 π}{6}

分式相乘:

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

= \frac{7 π 2}{6}

数字相乘:

7 \cdot 2 = 14

= \frac{14 π}{6}

约分:

2

= \frac{7 π}{3}

2 \cdot 2 πn = 4 πn

2 \cdot 2 πn

数字相乘:

2 \cdot 2 = 4

= 4 πn

= \frac{7 π}{3} + 4 πn

x = \frac{7 π}{3} + 4 πn

x = \frac{7 π}{3} + 4 πn

x = \frac{7 π}{3} + 4 πn

\frac{x}{2} = \frac{11 π}{6} + 2 πn : x = \frac{11 π}{3} + 4 πn

\frac{x}{2} = \frac{11 π}{6} + 2 πn

在两边乘以

2

\frac{x}{2} = \frac{11 π}{6} + 2 πn

在两边乘以

2

\frac{2 x}{2} = 2 \cdot \frac{11 π}{6} + 2 \cdot 2 πn

化简

\frac{2 x}{2} = 2 \cdot \frac{11 π}{6} + 2 \cdot 2 πn

化简

\frac{2 x}{2} : x

\frac{2 x}{2}

数字相除:

\frac{2}{2} = 1

= x

化简

2 \cdot \frac{11 π}{6} + 2 \cdot 2 πn : \frac{11 π}{3} + 4 πn

2 \cdot \frac{11 π}{6} + 2 \cdot 2 πn

2 \cdot \frac{11 π}{6} = \frac{11 π}{3}

2 \cdot \frac{11 π}{6}

分式相乘:

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

= \frac{11 π 2}{6}

数字相乘:

11 \cdot 2 = 22

= \frac{22 π}{6}

约分:

2

= \frac{11 π}{3}

2 \cdot 2 πn = 4 πn

2 \cdot 2 πn

数字相乘:

2 \cdot 2 = 4

= 4 πn

= \frac{11 π}{3} + 4 πn

x = \frac{11 π}{3} + 4 πn

x = \frac{11 π}{3} + 4 πn

x = \frac{11 π}{3} + 4 πn

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

\frac{x}{2} = \frac{π}{2} + 2 πn

在两边乘以

2

\frac{x}{2} = \frac{π}{2} + 2 πn

在两边乘以

2

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

化简

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

化简

\frac{2 x}{2} : x

\frac{2 x}{2}

数字相除:

\frac{2}{2} = 1

= x

化简

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

2 \cdot \frac{π}{2} + 2 \cdot 2 πn

2 \cdot \frac{π}{2} = π

2 \cdot \frac{π}{2}

分式相乘:

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

= \frac{π 2}{2}

约分:

2

= π

2 \cdot 2 πn = 4 πn

2 \cdot 2 πn

数字相乘:

2 \cdot 2 = 4

= 4 πn

= π + 4 πn

x = π + 4 πn

x = π + 4 πn

x = π + 4 πn

x = \frac{7 π}{3} + 4 πn, x = \frac{11 π}{3} + 4 πn, x = π + 4 πn

作图

流行的例子

sin^2(x)-sin(x)=2,0<= x<= 2pi

sin^{2} (x) - sin (x) = 2, 0 \leq x \leq 2 π

cos (θ) = \frac{33}{55}

cos(4x)cos(x)-sin(4x)sin(x)= 1/2

cos (4 x) cos (x) - sin (4 x) sin (x) = \frac{1}{2}

tan (θ) = \frac{7}{3}

cos(a)= 1/(sqrt(3))

cos (a) = \frac{1}{3}