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受欢迎的三角函数 >

tan(x)-sec(x)=1

解答

tan (x) - sec (x) = 1

解答

x = 2 πn + π

+1

度数

x = 18 0^{\circ} + 36 0^{\circ} n

求解步骤

tan (x) - sec (x) = 1

两边减去

1

tan (x) - sec (x) - 1 = 0

用 sin, cos 表示

- 1 - sec (x) + tan (x)

使用基本三角恒等式:

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

= - 1 - \frac{1}{cos ( x )} + tan (x)

使用基本三角恒等式:

tan (x) = \frac{sin ( x )}{cos ( x )}

= - 1 - \frac{1}{cos ( x )} + \frac{sin ( x )}{cos ( x )}

化简

- 1 - \frac{1}{cos ( x )} + \frac{sin ( x )}{cos ( x )} : \frac{- cos ( x ) - 1 + sin ( x )}{cos ( x )}

- 1 - \frac{1}{cos ( x )} + \frac{sin ( x )}{cos ( x )}

合并分式

- \frac{1}{cos ( x )} + \frac{sin ( x )}{cos ( x )} : \frac{- 1 + sin ( x )}{cos ( x )}

使用法则

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

= \frac{- 1 + sin ( x )}{cos ( x )}

= - 1 + \frac{sin ( x ) - 1}{cos ( x )}

将项转换为分式:

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

= - \frac{1 \cdot cos ( x )}{cos ( x )} + \frac{- 1 + sin ( x )}{cos ( x )}

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 cos ( x ) - 1 + sin ( x )}{cos ( x )}

乘以:

1 \cdot cos (x) = cos (x)

= \frac{- cos ( x ) - 1 + sin ( x )}{cos ( x )}

= \frac{- cos ( x ) - 1 + sin ( x )}{cos ( x )}

\frac{- 1 - cos ( x ) + sin ( x )}{cos ( x )} = 0

\frac{f ( x )}{g ( x )} = 0 \Rightarrow f (x) = 0

- 1 - cos (x) + sin (x) = 0

使用三角恒等式改写

- 1 - cos (x) + sin (x)

sin (x) - cos (x) = 2 sin (x - \frac{π}{4})

sin (x) - cos (x)

改写为

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

使用以下普通恒等式:

cos (\frac{π}{4}) = \frac{1}{2}

使用以下普通恒等式:

sin (\frac{π}{4}) = \frac{1}{2}

= 2 (cos (\frac{π}{4}) sin (x) - sin (\frac{π}{4}) cos (x))

使用角和恒等式:

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

= 2 sin (x - \frac{π}{4})

= - 1 + 2 sin (x - \frac{π}{4})

- 1 + 2 sin (x - \frac{π}{4}) = 0

将

1

到右边

- 1 + 2 sin (x - \frac{π}{4}) = 0

两边加上

1

- 1 + 2 sin (x - \frac{π}{4}) + 1 = 0 + 1

化简

2 sin (x - \frac{π}{4}) = 1

2 sin (x - \frac{π}{4}) = 1

两边除以

2

2 sin (x - \frac{π}{4}) = 1

两边除以

2

\frac{2 sin ( x - \frac{π}{4} )}{2} = \frac{1}{2}

化简

\frac{2 sin ( x - \frac{π}{4} )}{2} = \frac{1}{2}

化简

\frac{2 sin ( x - \frac{π}{4} )}{2} : sin (x - \frac{π}{4})

\frac{2 sin ( x - \frac{π}{4} )}{2}

约分:

2

= sin (x - \frac{π}{4})

化简

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

\frac{1}{2}

乘以共轭根式

\frac{2}{2}

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

1 \cdot 2 = 2

22 = 2

22

使用根式运算法则:

a a = a

22 = 2

= 2

= \frac{2}{2}

sin (x - \frac{π}{4}) = \frac{2}{2}

sin (x - \frac{π}{4}) = \frac{2}{2}

sin (x - \frac{π}{4}) = \frac{2}{2}

sin (x - \frac{π}{4}) = \frac{2}{2}

的通解

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}

x - \frac{π}{4} = \frac{π}{4} + 2 πn, x - \frac{π}{4} = \frac{3 π}{4} + 2 πn

x - \frac{π}{4} = \frac{π}{4} + 2 πn, x - \frac{π}{4} = \frac{3 π}{4} + 2 πn

解

x - \frac{π}{4} = \frac{π}{4} + 2 πn : x = \frac{π}{2} + 2 πn

x - \frac{π}{4} = \frac{π}{4} + 2 πn

将

\frac{π}{4}

到右边

x - \frac{π}{4} = \frac{π}{4} + 2 πn

两边加上

\frac{π}{4}

x - \frac{π}{4} + \frac{π}{4} = \frac{π}{4} + 2 πn + \frac{π}{4}

化简

x - \frac{π}{4} + \frac{π}{4} = \frac{π}{4} + 2 πn + \frac{π}{4}

化简

x - \frac{π}{4} + \frac{π}{4} : x

x - \frac{π}{4} + \frac{π}{4}

同类项相加:

- \frac{π}{4} + \frac{π}{4} = 0

= x

化简

\frac{π}{4} + 2 πn + \frac{π}{4} : \frac{π}{2} + 2 πn

\frac{π}{4} + 2 πn + \frac{π}{4}

对同类项分组

= \frac{π}{4} + \frac{π}{4} + 2 πn

合并分式

\frac{π}{4} + \frac{π}{4} : \frac{π}{2}

使用法则

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

= \frac{π + π}{4}

同类项相加:

π + π = 2 π

= \frac{2 π}{4}

约分:

2

= \frac{π}{2}

= \frac{π}{2} + 2 πn

x = \frac{π}{2} + 2 πn

x = \frac{π}{2} + 2 πn

x = \frac{π}{2} + 2 πn

解

x - \frac{π}{4} = \frac{3 π}{4} + 2 πn : x = 2 πn + π

x - \frac{π}{4} = \frac{3 π}{4} + 2 πn

将

\frac{π}{4}

到右边

x - \frac{π}{4} = \frac{3 π}{4} + 2 πn

两边加上

\frac{π}{4}

x - \frac{π}{4} + \frac{π}{4} = \frac{3 π}{4} + 2 πn + \frac{π}{4}

化简

x - \frac{π}{4} + \frac{π}{4} = \frac{3 π}{4} + 2 πn + \frac{π}{4}

化简

x - \frac{π}{4} + \frac{π}{4} : x

x - \frac{π}{4} + \frac{π}{4}

同类项相加:

- \frac{π}{4} + \frac{π}{4} = 0

= x

化简

\frac{3 π}{4} + 2 πn + \frac{π}{4} : 2 πn + π

\frac{3 π}{4} + 2 πn + \frac{π}{4}

对同类项分组

= 2 πn + \frac{π}{4} + \frac{3 π}{4}

合并分式

\frac{π}{4} + \frac{3 π}{4} : π

使用法则

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

= \frac{π + 3 π}{4}

同类项相加:

π + 3 π = 4 π

= \frac{4 π}{4}

数字相除:

\frac{4}{4} = 1

= π

= 2 πn + π

x = 2 πn + π

x = 2 πn + π

x = 2 πn + π

x = \frac{π}{2} + 2 πn, x = 2 πn + π

因为方程对以下值无定义:

\frac{π}{2} + 2 πn

x = 2 πn + π

作图

流行的例子

cos^2(x)+2cos(x)-2=0

cos^{2} (x) + 2 cos (x) - 2 = 0

- sin (4 x) \cdot 4 = 0

cos (θ) = \frac{5}{6}

cos(2x)=cos^2(x)-1/2

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

cos(x)=1,0<= x<= 2pi

cos (x) = 1, 0 \leq x \leq 2 π