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受欢迎的三角函数 >

sin^4(x)+2sin^2(x)-3=0

解答

sin^{4} (x) + 2 sin^{2} (x) - 3 = 0

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

sin^{4} (x) + 2 sin^{2} (x) - 3 = 0

用替代法求解

sin^{4} (x) + 2 sin^{2} (x) - 3 = 0

令

: sin (x) = u

u^{4} + 2 u^{2} - 3 = 0

u^{4} + 2 u^{2} - 3 = 0 : u = 1, u = - 1, u = 3 i, u = - 3 i

u^{4} + 2 u^{2} - 3 = 0

用

v = u^{2}

和

v^{2} = u^{4}

改写方程式

v^{2} + 2 v - 3 = 0

解

v^{2} + 2 v - 3 = 0 : v = 1, v = - 3

v^{2} + 2 v - 3 = 0

使用求根公式求解

v^{2} + 2 v - 3 = 0

二次方程求根公式:

若

a = 1, b = 2, c = - 3

v_{1, 2} = \frac{- 2 \pm 2 ^{2} - 4 \cdot 1 \cdot ( - 3 )}{2 \cdot 1}

v_{1, 2} = \frac{- 2 \pm 2 ^{2} - 4 \cdot 1 \cdot ( - 3 )}{2 \cdot 1}

2^{2} - 4 \cdot 1 \cdot (- 3) = 4

2^{2} - 4 \cdot 1 \cdot (- 3)

使用法则

- (- a) = a

= 2^{2} + 4 \cdot 1 \cdot 3

数字相乘:

4 \cdot 1 \cdot 3 = 12

= 2^{2} + 12

2^{2} = 4

= 4 + 12

数字相加:

4 + 12 = 16

= 16

因式分解数字:

16 = 4^{2}

= 4^{2}

使用根式运算法则:

n a^{n} = a

4^{2} = 4

= 4

v_{1, 2} = \frac{- 2 \pm 4}{2 \cdot 1}

将解分隔开

v_{1} = \frac{- 2 + 4}{2 \cdot 1}, v_{2} = \frac{- 2 - 4}{2 \cdot 1}

v = \frac{- 2 + 4}{2 \cdot 1} : 1

\frac{- 2 + 4}{2 \cdot 1}

数字相加/相减:

- 2 + 4 = 2

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

数字相乘:

2 \cdot 1 = 2

= \frac{2}{2}

使用法则

\frac{a}{a} = 1

= 1

v = \frac{- 2 - 4}{2 \cdot 1} : - 3

\frac{- 2 - 4}{2 \cdot 1}

数字相减:

- 2 - 4 = - 6

= \frac{- 6}{2 \cdot 1}

数字相乘:

2 \cdot 1 = 2

= \frac{- 6}{2}

使用分式法则:

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

= - \frac{6}{2}

数字相除:

\frac{6}{2} = 3

= - 3

二次方程组的解是:

v = 1, v = - 3

v = 1, v = - 3

代回

v = u^{2}

，求解

u

解

u^{2} = 1 : u = 1, u = - 1

u^{2} = 1

对于

x^{2} = f (a)

解为

x = f (a), - f (a)

u = 1, u = - 1

1 = 1

1

使用法则

1 = 1

= 1

- 1 = - 1

- 1

使用法则

1 = 1

= - 1

u = 1, u = - 1

解

u^{2} = - 3 : u = 3 i, u = - 3 i

u^{2} = - 3

对于

x^{2} = f (a)

解为

x = f (a), - f (a)

u = - 3, u = - - 3

化简

- 3 : 3 i

- 3

使用根式运算法则:

- a = - 1 a

- 3 = - 1 3

= - 1 3

使用虚数运算法则:

- 1 = i

= 3 i

化简

- - 3 : - 3 i

- - 3

化简

- 3 : 3 i

- 3

使用根式运算法则:

- a = - 1 a

- 3 = - 1 3

= - 1 3

使用虚数运算法则:

- 1 = i

= 3 i

= - 3 i

u = 3 i, u = - 3 i

解为

u = 1, u = - 1, u = 3 i, u = - 3 i

u = sin (x)

代回

sin (x) = 1, sin (x) = - 1, sin (x) = 3 i, sin (x) = - 3 i

sin (x) = 1, sin (x) = - 1, sin (x) = 3 i, sin (x) = - 3 i

sin (x) = 1 : x = \frac{π}{2} + 2 πn

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

sin (x) = - 1 : x = \frac{3 π}{2} + 2 πn

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{3 π}{2} + 2 πn

x = \frac{3 π}{2} + 2 πn

sin (x) = 3 i :

无解

sin (x) = 3 i

无解

sin (x) = - 3 i :

无解

sin (x) = - 3 i

无解

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

csc^2(θ)+2csc(θ)-24=0

csc^{2} (θ) + 2 csc (θ) - 24 = 0

2sin(θ)=2cos(2θ)

2 sin (θ) = 2 cos (2 θ)

2 cos^{2} (θ) = 1

sec(θ)=-(2sqrt(3))/3

sec (θ) = - \frac{2 3}{3}

cos (θ) = \frac{8}{17}