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受欢迎的三角函数 >

sec(285)

解答

sec (28 5^{\circ})

解答

2 (1 + 3)

+1

十进制

3.86370 \dots

求解步骤

sec (28 5^{\circ})

使用三角恒等式改写:

\frac{1}{cos ( 28 5 ^{\circ} )}

sec (28 5^{\circ})

使用基本三角恒等式:

sec (x) = \frac{1}{cos ( x )}

= \frac{1}{cos ( 28 5 ^{\circ} )}

= \frac{1}{cos ( 28 5 ^{\circ} )}

使用三角恒等式改写:

cos (28 5^{\circ}) = \frac{2 ( 3 - 1 )}{4}

cos (28 5^{\circ})

使用三角恒等式改写:

cos (15 0^{\circ}) cos (13 5^{\circ}) - sin (15 0^{\circ}) sin (13 5^{\circ})

cos (28 5^{\circ})

将

cos (28 5^{\circ})

写为

cos (15 0^{\circ} + 13 5^{\circ})

= cos (15 0^{\circ} + 13 5^{\circ})

使用角和恒等式:

cos (s + t) = cos (s) cos (t) - sin (s) sin (t)

= cos (15 0^{\circ}) cos (13 5^{\circ}) - sin (15 0^{\circ}) sin (13 5^{\circ})

= cos (15 0^{\circ}) cos (13 5^{\circ}) - sin (15 0^{\circ}) sin (13 5^{\circ})

使用以下普通恒等式:

cos (15 0^{\circ}) = - \frac{3}{2}

cos (15 0^{\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{3}{2}

使用以下普通恒等式:

cos (13 5^{\circ}) = - \frac{2}{2}

cos (13 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}

使用以下普通恒等式:

sin (15 0^{\circ}) = \frac{1}{2}

sin (15 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}

使用以下普通恒等式:

sin (13 5^{\circ}) = \frac{2}{2}

sin (13 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{3}{2}) (- \frac{2}{2}) - \frac{1}{2} \cdot \frac{2}{2}

化简

(- \frac{3}{2}) (- \frac{2}{2}) - \frac{1}{2} \cdot \frac{2}{2} : \frac{2 ( 3 - 1 )}{4}

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

去除括号:

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

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

因式分解出通项

\frac{2}{2}

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

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

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

使用法则

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

= \frac{3 - 1}{2}

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

分式相乘:

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

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

数字相乘:

2 \cdot 2 = 4

= \frac{2 ( 3 - 1 )}{4}

= \frac{2 ( 3 - 1 )}{4}

= \frac{1}{\frac{2 ( 3 - 1 )}{4}}

化简

\frac{1}{\frac{2 ( 3 - 1 )}{4}} : 2 (1 + 3)

\frac{1}{\frac{2 ( 3 - 1 )}{4}}

使用分式法则:

\frac{1}{\frac{b}{c}} = \frac{c}{b}

= \frac{4}{2 ( 3 - 1 )}

分解

4 : 2^{2}

因式分解

4 = 2^{2}

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

消掉

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

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

使用根式运算法则:

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

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

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

使用指数法则:

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

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

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

数字相减:

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

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

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

2^{\frac{3}{2}} = 22

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

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

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

使用指数法则:

x^{a + b} = x^{a} x^{b}

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

整理后得

= 22

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

\frac{2 2}{3 - 1}

有理化:

2 (1 + 3)

\frac{2 2}{3 - 1}

乘以共轭根式

\frac{3 + 1}{3 + 1}

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

(3 - 1) (3 + 1) = 2

(3 - 1) (3 + 1)

使用平方差公式:

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

a = 3, b = 1

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

化简

(3)^{2} - 1^{2} : 2

(3)^{2} - 1^{2}

使用法则

1^{a} = 1

1^{2} = 1

= (3)^{2} - 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

= 3 - 1

数字相减:

3 - 1 = 2

= 2

= 2

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

数字相除:

\frac{2}{2} = 1

= 2 (1 + 3)

= 2 (1 + 3)

= 2 (1 + 3)

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