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受欢迎的三角函数 >

(cos^4(x))/3 =sin^2(x)

解答

\frac{cos ^{4} ( x )}{3} = sin^{2} (x)

解答

x = - 0.47445 \dots + 2 πn, x = π + 0.47445 \dots + 2 πn, x = 0.47445 \dots + 2 πn, x = π - 0.47445 \dots + 2 πn

+1

度数

x = - 27.18404 \dots^{\circ} + 36 0^{\circ} n, x = 207.18404 \dots^{\circ} + 36 0^{\circ} n, x = 27.18404 \dots^{\circ} + 36 0^{\circ} n, x = 152.81595 \dots^{\circ} + 36 0^{\circ} n

求解步骤

\frac{cos ^{4} ( x )}{3} = sin^{2} (x)

两边减去

sin^{2} (x)

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

化简

\frac{cos ^{4} ( x )}{3} - sin^{2} (x) : \frac{cos ^{4} ( x ) - 3 sin ^{2} ( x )}{3}

\frac{cos ^{4} ( x )}{3} - sin^{2} (x)

将项转换为分式:

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

= \frac{cos ^{4} ( x )}{3} - \frac{sin ^{2} ( x ) \cdot 3}{3}

因为分母相等，所以合并分式:

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

= \frac{cos ^{4} ( x ) - sin ^{2} ( x ) \cdot 3}{3}

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

\frac{f ( x )}{g ( x )} = 0 \Rightarrow f (x) = 0

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

分解

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

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

将

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

改写为

(cos^{2} (x))^{2} - (3 sin (x))^{2}

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

使用根式运算法则:

a = (a)^{2}

3 = (3)^{2}

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

使用指数法则:

a^{b c} = (a^{b})^{c}

cos^{4} (x) = (cos^{2} (x))^{2}

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

使用指数法则:

a^{m} b^{m} = (ab)^{m}

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

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

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

使用平方差公式:

x^{2} - y^{2} = (x + y) (x - y)

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

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

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

分别求解每个部分

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

cos^{2} (x) + 3 sin (x) = 0 : x = arcsin (- \frac{- 3 + 7}{2}) + 2 πn, x = π + arcsin (\frac{- 3 + 7}{2}) + 2 πn

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

使用三角恒等式改写

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

使用毕达哥拉斯恒等式:

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

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

= 1 - sin^{2} (x) + sin (x) 3

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

用替代法求解

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

令

: sin (x) = u

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

1 - u^{2} + u 3 = 0 : u = - \frac{- 3 + 7}{2}, u = \frac{3 + 7}{2}

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

改写成标准形式

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

- u^{2} + 3 u + 1 = 0

使用求根公式求解

- u^{2} + 3 u + 1 = 0

二次方程求根公式:

若

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

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

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

(3)^{2} - 4 (- 1) \cdot 1 = 7

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

使用法则

- (- a) = a

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

(3)^{2} = 3

(3)^{2}

使用根式运算法则:

a = a^{\frac{1}{2}}

= (3^{\frac{1}{2}})^{2}

使用指数法则:

(a^{b})^{c} = a^{b c}

= 3^{\frac{1}{2} \cdot 2}

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

\frac{1}{2} \cdot 2

分式相乘:

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

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

约分:

2

= 1

= 3

4 \cdot 1 \cdot 1 = 4

4 \cdot 1 \cdot 1

数字相乘:

4 \cdot 1 \cdot 1 = 4

= 4

= 3 + 4

数字相加:

3 + 4 = 7

= 7

u_{1, 2} = \frac{- 3 \pm 7}{2 ( - 1 )}

将解分隔开

u_{1} = \frac{- 3 + 7}{2 ( - 1 )}, u_{2} = \frac{- 3 - 7}{2 ( - 1 )}

u = \frac{- 3 + 7}{2 ( - 1 )} : - \frac{- 3 + 7}{2}

\frac{- 3 + 7}{2 ( - 1 )}

去除括号:

(- a) = - a

= \frac{- 3 + 7}{- 2 \cdot 1}

数字相乘:

2 \cdot 1 = 2

= \frac{- 3 + 7}{- 2}

使用分式法则:

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

= - \frac{- 3 + 7}{2}

u = \frac{- 3 - 7}{2 ( - 1 )} : \frac{3 + 7}{2}

\frac{- 3 - 7}{2 ( - 1 )}

去除括号:

(- a) = - a

= \frac{- 3 - 7}{- 2 \cdot 1}

数字相乘:

2 \cdot 1 = 2

= \frac{- 3 - 7}{- 2}

使用分式法则:

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

- 3 - 7 = - (3 + 7)

= \frac{3 + 7}{2}

二次方程组的解是:

u = - \frac{- 3 + 7}{2}, u = \frac{3 + 7}{2}

u = sin (x)

代回

sin (x) = - \frac{- 3 + 7}{2}, sin (x) = \frac{3 + 7}{2}

sin (x) = - \frac{- 3 + 7}{2}, sin (x) = \frac{3 + 7}{2}

sin (x) = - \frac{- 3 + 7}{2} : x = arcsin (- \frac{- 3 + 7}{2}) + 2 πn, x = π + arcsin (\frac{- 3 + 7}{2}) + 2 πn

sin (x) = - \frac{- 3 + 7}{2}

使用反三角函数性质

sin (x) = - \frac{- 3 + 7}{2}

sin (x) = - \frac{- 3 + 7}{2}

的通解

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

x = arcsin (- \frac{- 3 + 7}{2}) + 2 πn, x = π + arcsin (\frac{- 3 + 7}{2}) + 2 πn

x = arcsin (- \frac{- 3 + 7}{2}) + 2 πn, x = π + arcsin (\frac{- 3 + 7}{2}) + 2 πn

sin (x) = \frac{3 + 7}{2} :

无解

sin (x) = \frac{3 + 7}{2}

- 1 \leq sin (x) \leq 1

无解

合并所有解

x = arcsin (- \frac{- 3 + 7}{2}) + 2 πn, x = π + arcsin (\frac{- 3 + 7}{2}) + 2 πn

cos^{2} (x) - 3 sin (x) = 0 : x = arcsin (\frac{7 - 3}{2}) + 2 πn, x = π - arcsin (\frac{7 - 3}{2}) + 2 πn

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

使用三角恒等式改写

cos^{2} (x) - sin (x) 3

使用毕达哥拉斯恒等式:

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

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

= 1 - sin^{2} (x) - sin (x) 3

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

用替代法求解

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

令

: sin (x) = u

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

1 - u^{2} - u 3 = 0 : u = - \frac{3 + 7}{2}, u = \frac{7 - 3}{2}

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

改写成标准形式

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

- u^{2} - 3 u + 1 = 0

使用求根公式求解

- u^{2} - 3 u + 1 = 0

二次方程求根公式:

若

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

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

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

(- 3)^{2} - 4 (- 1) \cdot 1 = 7

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

使用法则

- (- a) = a

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

(- 3)^{2} = 3

(- 3)^{2}

使用指数法则:

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

若

n

是偶数

(- 3)^{2} = (3)^{2}

= (3)^{2}

使用根式运算法则:

a = a^{\frac{1}{2}}

= (3^{\frac{1}{2}})^{2}

使用指数法则:

(a^{b})^{c} = a^{b c}

= 3^{\frac{1}{2} \cdot 2}

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

\frac{1}{2} \cdot 2

分式相乘:

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

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

约分:

2

= 1

= 3

4 \cdot 1 \cdot 1 = 4

4 \cdot 1 \cdot 1

数字相乘:

4 \cdot 1 \cdot 1 = 4

= 4

= 3 + 4

数字相加:

3 + 4 = 7

= 7

u_{1, 2} = \frac{- ( - 3 ) \pm 7}{2 ( - 1 )}

将解分隔开

u_{1} = \frac{- ( - 3 ) + 7}{2 ( - 1 )}, u_{2} = \frac{- ( - 3 ) - 7}{2 ( - 1 )}

u = \frac{- ( - 3 ) + 7}{2 ( - 1 )} : - \frac{3 + 7}{2}

\frac{- ( - 3 ) + 7}{2 ( - 1 )}

去除括号:

(- a) = - a, - (- a) = a

= \frac{3 + 7}{- 2 \cdot 1}

数字相乘:

2 \cdot 1 = 2

= \frac{3 + 7}{- 2}

使用分式法则:

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

= - \frac{3 + 7}{2}

u = \frac{- ( - 3 ) - 7}{2 ( - 1 )} : \frac{7 - 3}{2}

\frac{- ( - 3 ) - 7}{2 ( - 1 )}

去除括号:

(- a) = - a, - (- a) = a

= \frac{3 - 7}{- 2 \cdot 1}

数字相乘:

2 \cdot 1 = 2

= \frac{3 - 7}{- 2}

使用分式法则:

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

3 - 7 = - (7 - 3)

= \frac{7 - 3}{2}

二次方程组的解是:

u = - \frac{3 + 7}{2}, u = \frac{7 - 3}{2}

u = sin (x)

代回

sin (x) = - \frac{3 + 7}{2}, sin (x) = \frac{7 - 3}{2}

sin (x) = - \frac{3 + 7}{2}, sin (x) = \frac{7 - 3}{2}

sin (x) = - \frac{3 + 7}{2} :

无解

sin (x) = - \frac{3 + 7}{2}

- 1 \leq sin (x) \leq 1

无解

sin (x) = \frac{7 - 3}{2} : x = arcsin (\frac{7 - 3}{2}) + 2 πn, x = π - arcsin (\frac{7 - 3}{2}) + 2 πn

sin (x) = \frac{7 - 3}{2}

使用反三角函数性质

sin (x) = \frac{7 - 3}{2}

sin (x) = \frac{7 - 3}{2}

的通解

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

x = arcsin (\frac{7 - 3}{2}) + 2 πn, x = π - arcsin (\frac{7 - 3}{2}) + 2 πn

x = arcsin (\frac{7 - 3}{2}) + 2 πn, x = π - arcsin (\frac{7 - 3}{2}) + 2 πn

合并所有解

x = arcsin (\frac{7 - 3}{2}) + 2 πn, x = π - arcsin (\frac{7 - 3}{2}) + 2 πn

合并所有解

x = arcsin (- \frac{- 3 + 7}{2}) + 2 πn, x = π + arcsin (\frac{- 3 + 7}{2}) + 2 πn, x = arcsin (\frac{7 - 3}{2}) + 2 πn, x = π - arcsin (\frac{7 - 3}{2}) + 2 πn

以小数形式表示解

x = - 0.47445 \dots + 2 πn, x = π + 0.47445 \dots + 2 πn, x = 0.47445 \dots + 2 πn, x = π - 0.47445 \dots + 2 πn

作图

流行的例子

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