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受欢迎的三角函数 >

cos(67.5)sin(22.5)

解答

cos (67. 5^{\circ}) sin (22. 5^{\circ})

解答

\frac{2 - 2}{4}

+1

十进制

0.14644 \dots

求解步骤

cos (67. 5^{\circ}) sin (22. 5^{\circ})

使用三角恒等式改写:

\frac{sin ( 9 0 ^{\circ} ) - sin ( 4 5 ^{\circ} )}{2}

cos (67. 5^{\circ}) sin (22. 5^{\circ})

使用积化和差恒等式:

sin (s) cos (t) = \frac{1}{2} (sin (s + t) + sin (s - t))

= \frac{1}{2} (sin (22. 5^{\circ} + 67. 5^{\circ}) + sin (22. 5^{\circ} - 67. 5^{\circ}))

化简

= \frac{sin ( 9 0 ^{\circ} ) + sin ( - 4 5 ^{\circ} )}{2}

利用以下特性:

sin (- x) = - sin (x)

sin (- 4 5^{\circ}) = - sin (4 5^{\circ})

= \frac{sin ( 9 0 ^{\circ} ) - sin ( 4 5 ^{\circ} )}{2}

= \frac{sin ( 9 0 ^{\circ} ) - sin ( 4 5 ^{\circ} )}{2}

使用以下普通恒等式:

sin (9 0^{\circ}) = 1

sin (9 0^{\circ})

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

= 1

使用以下普通恒等式:

sin (4 5^{\circ}) = \frac{2}{2}

sin (4 5^{\circ})

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

= \frac{2}{2}

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

化简

\frac{1 - \frac{2}{2}}{2} : \frac{2 - 2}{4}

\frac{1 - \frac{2}{2}}{2}

化简

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

1 - \frac{2}{2}

将项转换为分式:

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

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

数字相乘:

1 \cdot 2 = 2

= \frac{2 - 2}{2}

分解

2 - 2 : 2 (2 - 1)

2 - 2

2 = 22

= 22 - 2

因式分解出通项

2

= 2 (2 - 1)

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

消掉

\frac{2 ( 2 - 1 )}{2} : \frac{2 - 1}{2}

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

使用根式运算法则:

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

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

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

使用指数法则:

\frac{x ^{a}}{x ^{b}} = \frac{1}{x ^{b - a}}

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

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

数字相减:

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

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

使用根式运算法则:

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

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

= \frac{2 - 1}{2}

= \frac{2 - 1}{2}

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

使用分式法则:

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

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

\frac{2 - 1}{2 2}

有理化:

\frac{2 - 2}{4}

\frac{2 - 1}{2 2}

乘以共轭根式

\frac{2}{2}

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

(2 - 1) 2 = 2 - 2

(2 - 1) 2

= 2 (2 - 1)

使用分配律:

a (b - c) = ab - a c

a = 2, b = 2, c = 1

= 22 - 2 \cdot 1

= 22 - 1 \cdot 2

化简

22 - 1 \cdot 2 : 2 - 2

22 - 1 \cdot 2

使用根式运算法则:

a a = a

22 = 2

= 2 - 1 \cdot 2

乘以:

1 \cdot 2 = 2

= 2 - 2

= 2 - 2

2 \cdot 22 = 4

2 \cdot 22

使用指数法则:

a^{b} \cdot a^{c} = a^{b + c}

222 = 2 \cdot 2^{\frac{1}{2}} \cdot 2^{\frac{1}{2}} = 2^{1 + \frac{1}{2} + \frac{1}{2}}

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

同类项相加:

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

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

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

= 2^{1 + 1}

数字相加:

1 + 1 = 2

= 2^{2}

2^{2} = 4

= 4

= \frac{2 - 2}{4}

= \frac{2 - 2}{4}

= \frac{2 - 2}{4}

流行的例子

tan (- \frac{10 π}{3})

csc (39 0^{\circ})

cos (2 \cdot \frac{π}{3})

arccsc (- 3)

sin(pi/3)+cos(pi/3)

sin (\frac{π}{3}) + cos (\frac{π}{3})