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受欢迎的三角函数 >

2sin^2(x)-7sin(x)=0

解答

2 sin^{2} (x) - 7 sin (x) = 0

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

2 sin^{2} (x) - 7 sin (x) = 0

用替代法求解

2 sin^{2} (x) - 7 sin (x) = 0

令

: sin (x) = u

2 u^{2} - 7 u = 0

2 u^{2} - 7 u = 0 : u = \frac{7}{2}, u = 0

2 u^{2} - 7 u = 0

使用求根公式求解

2 u^{2} - 7 u = 0

二次方程求根公式:

若

a = 2, b = - 7, c = 0

u_{1, 2} = \frac{- ( - 7 ) \pm ( - 7 ) ^{2} - 4 \cdot 2 \cdot 0}{2 \cdot 2}

u_{1, 2} = \frac{- ( - 7 ) \pm ( - 7 ) ^{2} - 4 \cdot 2 \cdot 0}{2 \cdot 2}

(- 7)^{2} - 4 \cdot 2 \cdot 0 = 7

(- 7)^{2} - 4 \cdot 2 \cdot 0

使用指数法则:

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

若

n

是偶数

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

= 7^{2} - 4 \cdot 2 \cdot 0

使用法则

0 \cdot a = 0

= 7^{2} - 0

7^{2} - 0 = 7^{2}

= 7^{2}

使用根式运算法则:

n a^{n} = a,

假定

a \geq 0

= 7

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

将解分隔开

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

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

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

使用法则

- (- a) = a

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

数字相加:

7 + 7 = 14

= \frac{14}{2 \cdot 2}

数字相乘:

2 \cdot 2 = 4

= \frac{14}{4}

约分:

2

= \frac{7}{2}

u = \frac{- ( - 7 ) - 7}{2 \cdot 2} : 0

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

使用法则

- (- a) = a

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

数字相减:

7 - 7 = 0

= \frac{0}{2 \cdot 2}

数字相乘:

2 \cdot 2 = 4

= \frac{0}{4}

使用法则

\frac{0}{a} = 0, a \neq = 0

= 0

二次方程组的解是:

u = \frac{7}{2}, u = 0

u = sin (x)

代回

sin (x) = \frac{7}{2}, sin (x) = 0

sin (x) = \frac{7}{2}, sin (x) = 0

sin (x) = \frac{7}{2} :

无解

sin (x) = \frac{7}{2}

- 1 \leq sin (x) \leq 1

无解

sin (x) = 0 : x = 2 πn, x = π + 2 πn

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

合并所有解

x = 2 πn, x = π + 2 πn

作图

流行的例子

sec (x) = \frac{1}{3}

solvefor x,u=cos(x^2y)

so l v e f or x, u = cos (x^{2} y)

6sin^2(x)-sin(x)cos(x)-2cos^2(x)=0

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

tan(θ)=(20(9.8))/(25)

tan (θ) = \frac{20 ( 9.8 )}{25}

solvefor t,0=8sin((pit)/(12))+32

so l v e f or t, 0 = 8 sin (\frac{π t}{12}) + 32