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受欢迎的三角函数 >

2cos^2(x)-sqrt(3)cos(x)=0,0<x<180

解答

2 cos^{2} (x) - 3 cos (x) = 0, 0^{\circ} < x < 18 0^{\circ}

解答

x = 3 0^{\circ}, x = 9 0^{\circ}

+1

弧度

x = \frac{π}{6}, x = \frac{π}{2}

求解步骤

2 cos^{2} (x) - 3 cos (x) = 0, 0^{\circ} < x < 18 0^{\circ}

用替代法求解

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

令

: cos (x) = u

2 u^{2} - 3 u = 0

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

2 u^{2} - 3 u = 0

使用求根公式求解

2 u^{2} - 3 u = 0

二次方程求根公式:

若

a = 2, b = - 3, c = 0

u_{1, 2} = \frac{- ( - 3 ) \pm ( - 3 ) ^{2} - 4 \cdot 2 \cdot 0}{2 \cdot 2}

u_{1, 2} = \frac{- ( - 3 ) \pm ( - 3 ) ^{2} - 4 \cdot 2 \cdot 0}{2 \cdot 2}

(- 3)^{2} - 4 \cdot 2 \cdot 0 = 3

(- 3)^{2} - 4 \cdot 2 \cdot 0

(- 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 2 \cdot 0 = 0

4 \cdot 2 \cdot 0

使用法则

0 \cdot a = 0

= 0

= 3 - 0

数字相减:

3 - 0 = 3

= 3

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

将解分隔开

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

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

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

使用法则

- (- a) = a

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

同类项相加:

3 + 3 = 23

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

数字相乘:

2 \cdot 2 = 4

= \frac{2 3}{4}

约分:

2

= \frac{3}{2}

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

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

使用法则

- (- a) = a

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

同类项相加:

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

u = cos (x)

代回

cos (x) = \frac{3}{2}, cos (x) = 0

cos (x) = \frac{3}{2}, cos (x) = 0

cos (x) = \frac{3}{2}, 0 < x < 18 0^{\circ} : x = 3 0^{\circ}

cos (x) = \frac{3}{2}, 0 < x < 18 0^{\circ}

cos (x) = \frac{3}{2}

的通解

cos (x)

周期表（周期为

36 0^{\circ} n

）：

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

x = 3 0^{\circ} + 36 0^{\circ} n, x = 33 0^{\circ} + 36 0^{\circ} n

x = 3 0^{\circ} + 36 0^{\circ} n, x = 33 0^{\circ} + 36 0^{\circ} n

在

0 < x < 18 0^{\circ}

范围内的解

x = 3 0^{\circ}

cos (x) = 0, 0 < x < 18 0^{\circ} : x = 9 0^{\circ}

cos (x) = 0, 0 < x < 18 0^{\circ}

cos (x) = 0

的通解

cos (x)

周期表（周期为

36 0^{\circ} n

）：

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

x = 9 0^{\circ} + 36 0^{\circ} n, x = 27 0^{\circ} + 36 0^{\circ} n

x = 9 0^{\circ} + 36 0^{\circ} n, x = 27 0^{\circ} + 36 0^{\circ} n

在

0 < x < 18 0^{\circ}

范围内的解

x = 9 0^{\circ}

合并所有解

x = 3 0^{\circ}, x = 9 0^{\circ}

作图

流行的例子

(tan(x))/(cos(x))= 2/3

tan(x)+2cos(x)csc(x)=sec(x)cos(x)+cot(x)

cos(a)=(sqrt(5))/5

5sec^2(x)-5=0,0<= x<2pi