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受欢迎的三角函数 >

(sin(30))/(sin(22.5))

解答

\frac{sin ( 3 0 ^{\circ} )}{sin ( 22. 5 ^{\circ} )}

解答

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

+1

十进制

1.30656 \dots

求解步骤

\frac{sin ( 3 0 ^{\circ} )}{sin ( 22. 5 ^{\circ} )}

使用以下普通恒等式:

sin (3 0^{\circ}) = \frac{1}{2}

sin (3 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}

= \frac{1}{2}

使用三角恒等式改写:

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

sin (22. 5^{\circ})

使用三角恒等式改写:

\frac{1 - cos ( 4 5 ^{\circ} )}{2}

sin (22. 5^{\circ})

将

sin (22. 5^{\circ})

写为

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

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

使用半角公式:

sin (\frac{θ}{2}) = \frac{1 - cos ( θ )}{2}

使用倍角公式

cos (2 θ) = 1 - 2 sin^{2} (θ)

用

\frac{θ}{2}

替代

θ

cos (θ) = 1 - 2 sin^{2} (\frac{θ}{2})

交换两边

2 sin^{2} (\frac{θ}{2}) = 1 - cos (θ)

两边除以

2

sin^{2} (\frac{θ}{2}) = \frac{( 1 - cos ( θ ) )}{2}

Square root both sides

Choose the root sign according to the quadrant of

\frac{θ}{2}

:

range [0, 9 0^{\circ}] [9 0^{\circ}, 18 0^{\circ}] [18 0^{\circ}, 27 0^{\circ}] [27 0^{\circ}, 36 0^{\circ}] quadrant I II III I V sin positive positive negative negative cos positive negative negative positive

sin (\frac{θ}{2}) = \frac{( 1 - cos ( θ ) )}{2}

= \frac{1 - cos ( 4 5 ^{\circ} )}{2}

= \frac{1 - cos ( 4 5 ^{\circ} )}{2}

使用以下普通恒等式:

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

cos (4 5^{\circ})

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}

= \frac{2}{2}

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

化简

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

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

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

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

化简

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

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

使用分式法则:

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

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

数字相乘:

2 \cdot 2 = 4

= \frac{2 - 2}{4}

= \frac{2 - 2}{4}

使用根式运算法则:

n \frac{a}{b} = \frac{n a}{n b},

假定

a \geq 0, b \geq 0

= \frac{2 - 2}{4}

4 = 2

4

因式分解数字:

4 = 2^{2}

= 2^{2}

使用根式运算法则:

n a^{n} = a

2^{2} = 2

= 2

= \frac{2 - 2}{2}

= \frac{2 - 2}{2}

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

化简

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

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

分式相除:

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

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

整理后得

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

约分:

2

= \frac{1}{2 - 2}

\frac{1}{2 - 2}

有理化:

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

\frac{1}{2 - 2}

乘以共轭根式

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

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

1 \cdot 2 - 2 = 2 - 2

2 - 2 2 - 2 = 2 - 2

2 - 2 2 - 2

使用根式运算法则:

a a = a

2 - 2 2 - 2 = 2 - 2

= 2 - 2

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

乘以共轭根式

\frac{2 + 2}{2 + 2}

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

(2 - 2) (2 + 2) = 2

(2 - 2) (2 + 2)

使用平方差公式:

(a - b) (a + b) = a^{2} - b^{2}

a = 2, b = 2

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

化简

2^{2} - (2)^{2} : 2

2^{2} - (2)^{2}

2^{2} = 4

2^{2}

2^{2} = 4

= 4

(2)^{2} = 2

(2)^{2}

使用根式运算法则:

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

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

使用指数法则:

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

= 2^{\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

= 2

= 4 - 2

数字相减:

4 - 2 = 2

= 2

= 2

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

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

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

流行的例子

cos^2((3pi)/8)+cos^2(pi/8)

cos^{2} (\frac{3 π}{8}) + cos^{2} (\frac{π}{8})

cos((3pi)/4)+sin((3pi)/4)

cos (\frac{3 π}{4}) + sin (\frac{3 π}{4})

tan^{2} (1921 4^{\circ})

arcsec(-1.0167)

arcsec (- 1.0167)

arctan (\frac{35}{65})