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受欢迎的三角函数 >

sec^2(x)-8sec(x)=0

解答

sec^{2} (x) - 8 sec (x) = 0

解答

x = 1.44546 \dots + 2 πn, x = 2 π - 1.44546 \dots + 2 πn

+1

度数

x = 82.81924 \dots^{\circ} + 36 0^{\circ} n, x = 277.18075 \dots^{\circ} + 36 0^{\circ} n

求解步骤

sec^{2} (x) - 8 sec (x) = 0

用替代法求解

sec^{2} (x) - 8 sec (x) = 0

令

: sec (x) = u

u^{2} - 8 u = 0

u^{2} - 8 u = 0 : u = 8, u = 0

u^{2} - 8 u = 0

使用求根公式求解

u^{2} - 8 u = 0

二次方程求根公式:

若

a = 1, b = - 8, c = 0

u_{1, 2} = \frac{- ( - 8 ) \pm ( - 8 ) ^{2} - 4 \cdot 1 \cdot 0}{2 \cdot 1}

u_{1, 2} = \frac{- ( - 8 ) \pm ( - 8 ) ^{2} - 4 \cdot 1 \cdot 0}{2 \cdot 1}

(- 8)^{2} - 4 \cdot 1 \cdot 0 = 8

(- 8)^{2} - 4 \cdot 1 \cdot 0

使用指数法则:

(- a)^{n} = a^{n},

若

n

是偶数

(- 8)^{2} = 8^{2}

= 8^{2} - 4 \cdot 1 \cdot 0

使用法则

0 \cdot a = 0

= 8^{2} - 0

8^{2} - 0 = 8^{2}

= 8^{2}

使用根式运算法则:

n a^{n} = a,

假定

a \geq 0

= 8

u_{1, 2} = \frac{- ( - 8 ) \pm 8}{2 \cdot 1}

将解分隔开

u_{1} = \frac{- ( - 8 ) + 8}{2 \cdot 1}, u_{2} = \frac{- ( - 8 ) - 8}{2 \cdot 1}

u = \frac{- ( - 8 ) + 8}{2 \cdot 1} : 8

\frac{- ( - 8 ) + 8}{2 \cdot 1}

使用法则

- (- a) = a

= \frac{8 + 8}{2 \cdot 1}

数字相加:

8 + 8 = 16

= \frac{16}{2 \cdot 1}

数字相乘:

2 \cdot 1 = 2

= \frac{16}{2}

数字相除:

\frac{16}{2} = 8

= 8

u = \frac{- ( - 8 ) - 8}{2 \cdot 1} : 0

\frac{- ( - 8 ) - 8}{2 \cdot 1}

使用法则

- (- a) = a

= \frac{8 - 8}{2 \cdot 1}

数字相减:

8 - 8 = 0

= \frac{0}{2 \cdot 1}

数字相乘:

2 \cdot 1 = 2

= \frac{0}{2}

使用法则

\frac{0}{a} = 0, a \neq = 0

= 0

二次方程组的解是:

u = 8, u = 0

u = sec (x)

代回

sec (x) = 8, sec (x) = 0

sec (x) = 8, sec (x) = 0

sec (x) = 8 : x = arcsec (8) + 2 πn, x = 2 π - arcsec (8) + 2 πn

sec (x) = 8

使用反三角函数性质

sec (x) = 8

sec (x) = 8

的通解

sec (x) = a \Rightarrow x = arcsec (a) + 2 πn, x = 2 π - arcsec (a) + 2 πn

x = arcsec (8) + 2 πn, x = 2 π - arcsec (8) + 2 πn

x = arcsec (8) + 2 πn, x = 2 π - arcsec (8) + 2 πn

sec (x) = 0 :

无解

sec (x) = 0

sec (x) \leq - 1 or sec (x) \geq 1

无解

合并所有解

x = arcsec (8) + 2 πn, x = 2 π - arcsec (8) + 2 πn

以小数形式表示解

x = 1.44546 \dots + 2 πn, x = 2 π - 1.44546 \dots + 2 πn

作图

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