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受欢迎的三角函数 >

(cos(pi/2)-cos((4pi)/3))/(2sin((5pi)/6))

解答

\frac{cos ( \frac{π}{2} ) - cos ( \frac{4 π}{3} )}{2 sin ( \frac{5 π}{6} )}

解答

\frac{1}{2}

+1

十进制

0.5

求解步骤

\frac{cos ( \frac{π}{2} ) - cos ( \frac{4 π}{3} )}{2 sin ( \frac{5 π}{6} )}

使用三角恒等式改写:

cos (\frac{4 π}{3}) = 1 - 2 sin^{2} (\frac{2 π}{3})

cos (\frac{4 π}{3})

将

cos (\frac{4 π}{3})

写为

cos (2 \cdot \frac{2 π}{3})

= cos (2 \cdot \frac{2 π}{3})

使用倍角公式:

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

= 1 - 2 sin^{2} (\frac{2 π}{3})

= \frac{cos ( \frac{π}{2} ) - ( 1 - 2 sin ^{2} ( \frac{2 π}{3} ) )}{2 sin ( \frac{5 π}{6} )}

化简

= \frac{cos ( \frac{π}{2} ) - 1 + 2 sin ^{2} ( \frac{2 π}{3} )}{2 sin ( \frac{5 π}{6} )}

使用以下普通恒等式:

cos (\frac{π}{2}) = 0

cos (\frac{π}{2})

cos (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} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{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} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= 0

使用以下普通恒等式:

sin (\frac{2 π}{3}) = \frac{3}{2}

sin (\frac{2 π}{3})

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}

= \frac{3}{2}

使用以下普通恒等式:

sin (\frac{5 π}{6}) = \frac{1}{2}

sin (\frac{5 π}{6})

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}

= \frac{1}{2}

= \frac{0 - 1 + 2 ( \frac{3}{2} ) ^{2}}{2 \cdot \frac{1}{2}}

化简

\frac{0 - 1 + 2 ( \frac{3}{2} ) ^{2}}{2 \cdot \frac{1}{2}} : \frac{1}{2}

\frac{0 - 1 + 2 ( \frac{3}{2} ) ^{2}}{2 \cdot \frac{1}{2}}

数字相减:

0 - 1 = - 1

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

乘

2 \cdot \frac{1}{2} : 1

2 \cdot \frac{1}{2}

分式相乘:

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

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

约分:

2

= 1

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

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

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

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

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

使用指数法则:

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

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

(3)^{2} : 3

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

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

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

分式相乘:

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

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

数字相乘:

3 \cdot 2 = 6

= \frac{6}{2 ^{2}}

分解

6 : 2 \cdot 3

因式分解

6 = 2 \cdot 3

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

约分:

2

= \frac{3}{2}

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

化简

\frac{3}{2} - 1 : \frac{1}{2}

\frac{3}{2} - 1

将项转换为分式:

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

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

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{3 - 1 \cdot 2}{2}

3 - 1 \cdot 2 = 1

3 - 1 \cdot 2

数字相乘:

1 \cdot 2 = 2

= 3 - 2

数字相减:

3 - 2 = 1

= 1

= \frac{1}{2}

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

使用分式法则:

\frac{a}{1} = a

= \frac{1}{2}

= \frac{1}{2}

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