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受欢迎的三角函数 >

6sin^2(θ)-10sin(θ)-8=-3sin(θ)-3

解答

6 sin^{2} (θ) - 10 sin (θ) - 8 = - 3 sin (θ) - 3

解答

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

+1

度数

θ = 21 0^{\circ} + 36 0^{\circ} n, θ = 33 0^{\circ} + 36 0^{\circ} n

求解步骤

6 sin^{2} (θ) - 10 sin (θ) - 8 = - 3 sin (θ) - 3

用替代法求解

6 sin^{2} (θ) - 10 sin (θ) - 8 = - 3 sin (θ) - 3

令

: sin (θ) = u

6 u^{2} - 10 u - 8 = - 3 u - 3

6 u^{2} - 10 u - 8 = - 3 u - 3 : u = \frac{5}{3}, u = - \frac{1}{2}

6 u^{2} - 10 u - 8 = - 3 u - 3

将

3

para o lado esquerdo

6 u^{2} - 10 u - 8 = - 3 u - 3

两边加上

3

6 u^{2} - 10 u - 8 + 3 = - 3 u - 3 + 3

化简

6 u^{2} - 10 u - 5 = - 3 u

6 u^{2} - 10 u - 5 = - 3 u

将

3 u

para o lado esquerdo

6 u^{2} - 10 u - 5 = - 3 u

两边加上

3 u

6 u^{2} - 10 u - 5 + 3 u = - 3 u + 3 u

化简

6 u^{2} - 7 u - 5 = 0

6 u^{2} - 7 u - 5 = 0

使用求根公式求解

6 u^{2} - 7 u - 5 = 0

二次方程求根公式:

若

a = 6, b = - 7, c = - 5

u_{1, 2} = \frac{- ( - 7 ) \pm ( - 7 ) ^{2} - 4 \cdot 6 ( - 5 )}{2 \cdot 6}

u_{1, 2} = \frac{- ( - 7 ) \pm ( - 7 ) ^{2} - 4 \cdot 6 ( - 5 )}{2 \cdot 6}

(- 7)^{2} - 4 \cdot 6 (- 5) = 13

(- 7)^{2} - 4 \cdot 6 (- 5)

使用法则

- (- a) = a

= (- 7)^{2} + 4 \cdot 6 \cdot 5

使用指数法则:

(- a)^{n} = a^{n},

若

n

是偶数

(- 7)^{2} = 7^{2}

= 7^{2} + 4 \cdot 6 \cdot 5

数字相乘:

4 \cdot 6 \cdot 5 = 120

= 7^{2} + 120

7^{2} = 49

= 49 + 120

数字相加:

49 + 120 = 169

= 169

因式分解数字:

169 = 1 3^{2}

= 1 3^{2}

使用根式运算法则:

n a^{n} = a

1 3^{2} = 13

= 13

u_{1, 2} = \frac{- ( - 7 ) \pm 13}{2 \cdot 6}

将解分隔开

u_{1} = \frac{- ( - 7 ) + 13}{2 \cdot 6}, u_{2} = \frac{- ( - 7 ) - 13}{2 \cdot 6}

u = \frac{- ( - 7 ) + 13}{2 \cdot 6} : \frac{5}{3}

\frac{- ( - 7 ) + 13}{2 \cdot 6}

使用法则

- (- a) = a

= \frac{7 + 13}{2 \cdot 6}

数字相加:

7 + 13 = 20

= \frac{20}{2 \cdot 6}

数字相乘:

2 \cdot 6 = 12

= \frac{20}{12}

约分:

4

= \frac{5}{3}

u = \frac{- ( - 7 ) - 13}{2 \cdot 6} : - \frac{1}{2}

\frac{- ( - 7 ) - 13}{2 \cdot 6}

使用法则

- (- a) = a

= \frac{7 - 13}{2 \cdot 6}

数字相减:

7 - 13 = - 6

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

数字相乘:

2 \cdot 6 = 12

= \frac{- 6}{12}

使用分式法则:

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

= - \frac{6}{12}

约分:

6

= - \frac{1}{2}

二次方程组的解是:

u = \frac{5}{3}, u = - \frac{1}{2}

u = sin (θ)

代回

sin (θ) = \frac{5}{3}, sin (θ) = - \frac{1}{2}

sin (θ) = \frac{5}{3}, sin (θ) = - \frac{1}{2}

sin (θ) = \frac{5}{3} :

无解

sin (θ) = \frac{5}{3}

- 1 \leq sin (x) \leq 1

无解

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

sin (θ) = - \frac{1}{2}

sin (θ) = - \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}

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

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

合并所有解

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

作图

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