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受欢迎的三角函数 >

3sin^2(x)=sin(x)+2

解答

3 sin^{2} (x) = sin (x) + 2

解答

x = \frac{π}{2} + 2 πn, x = - 0.72972 \dots + 2 πn, x = π + 0.72972 \dots + 2 πn

+1

度数

x = 9 0^{\circ} + 36 0^{\circ} n, x = - 41.81031 \dots^{\circ} + 36 0^{\circ} n, x = 221.81031 \dots^{\circ} + 36 0^{\circ} n

求解步骤

3 sin^{2} (x) = sin (x) + 2

用替代法求解

3 sin^{2} (x) = sin (x) + 2

令

: sin (x) = u

3 u^{2} = u + 2

3 u^{2} = u + 2 : u = 1, u = - \frac{2}{3}

3 u^{2} = u + 2

将

2

para o lado esquerdo

3 u^{2} = u + 2

两边减去

2

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

化简

3 u^{2} - 2 = u

3 u^{2} - 2 = u

将

u

para o lado esquerdo

3 u^{2} - 2 = u

两边减去

u

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

化简

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

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

改写成标准形式

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

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

使用求根公式求解

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

二次方程求根公式:

若

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

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

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

(- 1)^{2} - 4 \cdot 3 (- 2) = 5

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

使用法则

- (- a) = a

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

(- 1)^{2} = 1

(- 1)^{2}

使用指数法则:

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

若

n

是偶数

(- 1)^{2} = 1^{2}

= 1^{2}

使用法则

1^{a} = 1

= 1

4 \cdot 3 \cdot 2 = 24

4 \cdot 3 \cdot 2

数字相乘:

4 \cdot 3 \cdot 2 = 24

= 24

= 1 + 24

数字相加:

1 + 24 = 25

= 25

因式分解数字:

25 = 5^{2}

= 5^{2}

使用根式运算法则:

n a^{n} = a

5^{2} = 5

= 5

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

将解分隔开

u_{1} = \frac{- ( - 1 ) + 5}{2 \cdot 3}, u_{2} = \frac{- ( - 1 ) - 5}{2 \cdot 3}

u = \frac{- ( - 1 ) + 5}{2 \cdot 3} : 1

\frac{- ( - 1 ) + 5}{2 \cdot 3}

使用法则

- (- a) = a

= \frac{1 + 5}{2 \cdot 3}

数字相加:

1 + 5 = 6

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

数字相乘:

2 \cdot 3 = 6

= \frac{6}{6}

使用法则

\frac{a}{a} = 1

= 1

u = \frac{- ( - 1 ) - 5}{2 \cdot 3} : - \frac{2}{3}

\frac{- ( - 1 ) - 5}{2 \cdot 3}

使用法则

- (- a) = a

= \frac{1 - 5}{2 \cdot 3}

数字相减:

1 - 5 = - 4

= \frac{- 4}{2 \cdot 3}

数字相乘:

2 \cdot 3 = 6

= \frac{- 4}{6}

使用分式法则:

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

= - \frac{4}{6}

约分:

2

= - \frac{2}{3}

二次方程组的解是:

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

u = sin (x)

代回

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

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

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) = - \frac{2}{3} : x = arcsin (- \frac{2}{3}) + 2 πn, x = π + arcsin (\frac{2}{3}) + 2 πn

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

使用反三角函数性质

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

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

的通解

sin (x) = - a \Rightarrow x = arcsin (- a) + 2 πn, x = π + arcsin (a) + 2 πn

x = arcsin (- \frac{2}{3}) + 2 πn, x = π + arcsin (\frac{2}{3}) + 2 πn

x = arcsin (- \frac{2}{3}) + 2 πn, x = π + arcsin (\frac{2}{3}) + 2 πn

合并所有解

x = \frac{π}{2} + 2 πn, x = arcsin (- \frac{2}{3}) + 2 πn, x = π + arcsin (\frac{2}{3}) + 2 πn

以小数形式表示解

x = \frac{π}{2} + 2 πn, x = - 0.72972 \dots + 2 πn, x = π + 0.72972 \dots + 2 πn

作图

流行的例子

sin(θ)=-7/25 ,cos(θ/2),270<θ<360

sin (θ) = - \frac{7}{25}, cos (\frac{θ}{2}), 27 0^{\circ} < θ < 36 0^{\circ}

3cos((2pit)/3)+10=11

3 cos (\frac{2 π t}{3}) + 10 = 11

9 sec^{2} (x) - 9 = 0

4tan(x)-7=3tan(x)-6

4 tan (x) - 7 = 3 tan (x) - 6

2 sin^{2} (x) + 1 = 0