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受欢迎的三角函数 >

2sin(2x)-3-6/(sin(2x)-1)=0

解答

2 sin (2 x) - 3 - \frac{6}{sin ( 2 x ) - 1} = 0

解答

x = \frac{7 π}{12} + πn, x = \frac{11 π}{12} + πn

+1

度数

x = 10 5^{\circ} + 18 0^{\circ} n, x = 16 5^{\circ} + 18 0^{\circ} n

求解步骤

2 sin (2 x) - 3 - \frac{6}{sin ( 2 x ) - 1} = 0

用替代法求解

2 sin (2 x) - 3 - \frac{6}{sin ( 2 x ) - 1} = 0

令

: sin (2 x) = u

2 u - 3 - \frac{6}{u - 1} = 0

2 u - 3 - \frac{6}{u - 1} = 0 : u = 3, u = - \frac{1}{2}

2 u - 3 - \frac{6}{u - 1} = 0

在两边乘以

u - 1

2 u - 3 - \frac{6}{u - 1} = 0

在两边乘以

u - 1

2 u (u - 1) - 3 (u - 1) - \frac{6}{u - 1} (u - 1) = 0 \cdot (u - 1)

化简

2 u (u - 1) - 3 (u - 1) - \frac{6}{u - 1} (u - 1) = 0 \cdot (u - 1)

化简

- \frac{6}{u - 1} (u - 1) : - 6

- \frac{6}{u - 1} (u - 1)

分式相乘:

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

= - \frac{6 ( u - 1 )}{u - 1}

约分:

u - 1

= - 6

化简

0 \cdot (u - 1) : 0

0 \cdot (u - 1)

使用法则

0 \cdot a = 0

= 0

2 u (u - 1) - 3 (u - 1) - 6 = 0

2 u (u - 1) - 3 (u - 1) - 6 = 0

2 u (u - 1) - 3 (u - 1) - 6 = 0

解

2 u (u - 1) - 3 (u - 1) - 6 = 0 : u = 3, u = - \frac{1}{2}

2 u (u - 1) - 3 (u - 1) - 6 = 0

展开

2 u (u - 1) - 3 (u - 1) - 6 : 2 u^{2} - 5 u - 3

2 u (u - 1) - 3 (u - 1) - 6

乘开

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

2 u (u - 1)

使用分配律:

a (b - c) = ab - a c

a = 2 u, b = u, c = 1

= 2 uu - 2 u \cdot 1

= 2 uu - 2 \cdot 1 \cdot u

化简

2 uu - 2 \cdot 1 \cdot u : 2 u^{2} - 2 u

2 uu - 2 \cdot 1 \cdot u

2 uu = 2 u^{2}

2 uu

使用指数法则:

a^{b} \cdot a^{c} = a^{b + c}

uu = u^{1 + 1}

= 2 u^{1 + 1}

数字相加:

1 + 1 = 2

= 2 u^{2}

2 \cdot 1 \cdot u = 2 u

2 \cdot 1 \cdot u

数字相乘:

2 \cdot 1 = 2

= 2 u

= 2 u^{2} - 2 u

= 2 u^{2} - 2 u

= 2 u^{2} - 2 u - 3 (u - 1) - 6

乘开

- 3 (u - 1) : - 3 u + 3

- 3 (u - 1)

使用分配律:

a (b - c) = ab - a c

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

= - 3 u - (- 3) \cdot 1

使用加减运算法则

- (- a) = a

= - 3 u + 3 \cdot 1

数字相乘:

3 \cdot 1 = 3

= - 3 u + 3

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

化简

2 u^{2} - 2 u - 3 u + 3 - 6 : 2 u^{2} - 5 u - 3

2 u^{2} - 2 u - 3 u + 3 - 6

同类项相加:

- 2 u - 3 u = - 5 u

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

数字相加/相减:

3 - 6 = - 3

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

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

2 u^{2} - 5 u - 3 = 0

使用求根公式求解

2 u^{2} - 5 u - 3 = 0

二次方程求根公式:

若

a = 2, b = - 5, c = - 3

u_{1, 2} = \frac{- ( - 5 ) \pm ( - 5 ) ^{2} - 4 \cdot 2 ( - 3 )}{2 \cdot 2}

u_{1, 2} = \frac{- ( - 5 ) \pm ( - 5 ) ^{2} - 4 \cdot 2 ( - 3 )}{2 \cdot 2}

(- 5)^{2} - 4 \cdot 2 (- 3) = 7

(- 5)^{2} - 4 \cdot 2 (- 3)

使用法则

- (- a) = a

= (- 5)^{2} + 4 \cdot 2 \cdot 3

使用指数法则:

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

若

n

是偶数

(- 5)^{2} = 5^{2}

= 5^{2} + 4 \cdot 2 \cdot 3

数字相乘:

4 \cdot 2 \cdot 3 = 24

= 5^{2} + 24

5^{2} = 25

= 25 + 24

数字相加:

25 + 24 = 49

= 49

因式分解数字:

49 = 7^{2}

= 7^{2}

使用根式运算法则:

n a^{n} = a

7^{2} = 7

= 7

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

将解分隔开

u_{1} = \frac{- ( - 5 ) + 7}{2 \cdot 2}, u_{2} = \frac{- ( - 5 ) - 7}{2 \cdot 2}

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

\frac{- ( - 5 ) + 7}{2 \cdot 2}

使用法则

- (- a) = a

= \frac{5 + 7}{2 \cdot 2}

数字相加:

5 + 7 = 12

= \frac{12}{2 \cdot 2}

数字相乘:

2 \cdot 2 = 4

= \frac{12}{4}

数字相除:

\frac{12}{4} = 3

= 3

u = \frac{- ( - 5 ) - 7}{2 \cdot 2} : - \frac{1}{2}

\frac{- ( - 5 ) - 7}{2 \cdot 2}

使用法则

- (- a) = a

= \frac{5 - 7}{2 \cdot 2}

数字相减:

5 - 7 = - 2

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

数字相乘:

2 \cdot 2 = 4

= \frac{- 2}{4}

使用分式法则:

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

= - \frac{2}{4}

约分:

2

= - \frac{1}{2}

二次方程组的解是:

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

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

验证解

找到无定义的点（奇点）:

u = 1

取

2 u - 3 - \frac{6}{u - 1}

的分母，令其等于零

解

u - 1 = 0 : u = 1

u - 1 = 0

将

1

到右边

u - 1 = 0

两边加上

1

u - 1 + 1 = 0 + 1

化简

u = 1

u = 1

以下点无定义

u = 1

将不在定义域的点与解相综合:

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

u = sin (2 x)

代回

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

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

sin (2 x) = 3 :

无解

sin (2 x) = 3

- 1 \leq sin (x) \leq 1

无解

sin (2 x) = - \frac{1}{2} : x = \frac{7 π}{12} + πn, x = \frac{11 π}{12} + πn

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

sin (2 x) = - \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}

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

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

解

2 x = \frac{7 π}{6} + 2 πn : x = \frac{7 π}{12} + πn

2 x = \frac{7 π}{6} + 2 πn

两边除以

2

2 x = \frac{7 π}{6} + 2 πn

两边除以

2

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

化简

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

化简

\frac{2 x}{2} : x

\frac{2 x}{2}

数字相除:

\frac{2}{2} = 1

= x

化简

\frac{\frac{7 π}{6}}{2} + \frac{2 πn}{2} : \frac{7 π}{12} + πn

\frac{\frac{7 π}{6}}{2} + \frac{2 πn}{2}

\frac{\frac{7 π}{6}}{2} = \frac{7 π}{12}

\frac{\frac{7 π}{6}}{2}

使用分式法则:

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

= \frac{7 π}{6 \cdot 2}

数字相乘:

6 \cdot 2 = 12

= \frac{7 π}{12}

\frac{2 πn}{2} = πn

\frac{2 πn}{2}

数字相除:

\frac{2}{2} = 1

= πn

= \frac{7 π}{12} + πn

x = \frac{7 π}{12} + πn

x = \frac{7 π}{12} + πn

x = \frac{7 π}{12} + πn

解

2 x = \frac{11 π}{6} + 2 πn : x = \frac{11 π}{12} + πn

2 x = \frac{11 π}{6} + 2 πn

两边除以

2

2 x = \frac{11 π}{6} + 2 πn

两边除以

2

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

化简

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

化简

\frac{2 x}{2} : x

\frac{2 x}{2}

数字相除:

\frac{2}{2} = 1

= x

化简

\frac{\frac{11 π}{6}}{2} + \frac{2 πn}{2} : \frac{11 π}{12} + πn

\frac{\frac{11 π}{6}}{2} + \frac{2 πn}{2}

\frac{\frac{11 π}{6}}{2} = \frac{11 π}{12}

\frac{\frac{11 π}{6}}{2}

使用分式法则:

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

= \frac{11 π}{6 \cdot 2}

数字相乘:

6 \cdot 2 = 12

= \frac{11 π}{12}

\frac{2 πn}{2} = πn

\frac{2 πn}{2}

数字相除:

\frac{2}{2} = 1

= πn

= \frac{11 π}{12} + πn

x = \frac{11 π}{12} + πn

x = \frac{11 π}{12} + πn

x = \frac{11 π}{12} + πn

x = \frac{7 π}{12} + πn, x = \frac{11 π}{12} + πn

合并所有解

x = \frac{7 π}{12} + πn, x = \frac{11 π}{12} + πn

作图

流行的例子

3sin^2(x)+11sin(x)+10=0

3 sin^{2} (x) + 11 sin (x) + 10 = 0

cos(x)(cos(x)+5)=2sin^2(x)

cos (x) (cos (x) + 5) = 2 sin^{2} (x)

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

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

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

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

cos^2(x)+3cos(x)=1

cos^{2} (x) + 3 cos (x) = 1