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受欢迎的三角函数 >

cos(x)-sin(x)=sqrt(2)

解答

cos (x) - sin (x) = 2

解答

x = \frac{7 π}{4} + 2 πn

+1

度数

x = 31 5^{\circ} + 36 0^{\circ} n

求解步骤

cos (x) - sin (x) = 2

两边减去

2

cos (x) - sin (x) - 2 = 0

使用三角恒等式改写

cos (x) - sin (x) - 2

利用以下特性:

sin (x) = cos (\frac{π}{2} - x)

= cos (x) - cos (\frac{π}{2} - x) - 2

使用和差化积恒等式:

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

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

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

2 sin (\frac{x + \frac{π}{2} - x}{2}) sin (\frac{x - ( \frac{π}{2} - x )}{2})

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

\frac{x + \frac{π}{2} - x}{2}

x + \frac{π}{2} - x = \frac{π}{2}

x + \frac{π}{2} - x

对同类项分组

= x - x + \frac{π}{2}

同类项相加:

x - x = 0

= \frac{π}{2}

= \frac{\frac{π}{2}}{2}

使用分式法则:

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

= \frac{π}{2 \cdot 2}

数字相乘:

2 \cdot 2 = 4

= \frac{π}{4}

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

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

\frac{x - ( \frac{π}{2} - x )}{2}

乘开

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

x - (\frac{π}{2} - x)

- (\frac{π}{2} - x) : - \frac{π}{2} + x

- (\frac{π}{2} - x)

打开括号

= - (\frac{π}{2}) - (- x)

使用加减运算法则

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

= - \frac{π}{2} + x

= x - \frac{π}{2} + x

化简

x - \frac{π}{2} + x : 2 x - \frac{π}{2}

x - \frac{π}{2} + x

对同类项分组

= x + x - \frac{π}{2}

同类项相加:

x + x = 2 x

= 2 x - \frac{π}{2}

= 2 x - \frac{π}{2}

= \frac{2 x - \frac{π}{2}}{2}

化简

2 x - \frac{π}{2} : \frac{4 x - π}{2}

2 x - \frac{π}{2}

将项转换为分式:

2 x = \frac{2 x 2}{2}

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

数字相乘:

2 \cdot 2 = 4

= \frac{4 x - π}{2}

= \frac{\frac{4 x - π}{2}}{2}

使用分式法则:

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

= \frac{4 x - π}{2 \cdot 2}

数字相乘:

2 \cdot 2 = 4

= \frac{4 x - π}{4}

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

化简

sin (\frac{π}{4}) : \frac{2}{2}

sin (\frac{π}{4})

使用以下普通恒等式:

sin (\frac{π}{4}) = \frac{2}{2}

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}

= \frac{2}{2}

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

分式相乘:

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

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

约分:

2

= 2 sin (\frac{4 x - π}{4})

= - 2 - 2 sin (\frac{4 x - π}{4})

- 2 - 2 sin (\frac{4 x - π}{4}) = 0

将

2

到右边

- 2 - 2 sin (\frac{4 x - π}{4}) = 0

两边加上

2

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

化简

- 2 sin (\frac{4 x - π}{4}) = 2

- 2 sin (\frac{4 x - π}{4}) = 2

两边除以

- 2

- 2 sin (\frac{4 x - π}{4}) = 2

两边除以

- 2

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

化简

sin (\frac{4 x - π}{4}) = - 1

sin (\frac{4 x - π}{4}) = - 1

sin (\frac{4 x - π}{4}) = - 1

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}

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

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

解

\frac{4 x - π}{4} = \frac{3 π}{2} + 2 πn : x = \frac{7 π}{4} + 2 πn

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

在两边乘以

4

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

在两边乘以

4

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

化简

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

化简

\frac{4 ( 4 x - π )}{4} : 4 x - π

\frac{4 ( 4 x - π )}{4}

数字相除:

\frac{4}{4} = 1

= 4 x - π

化简

4 \cdot \frac{3 π}{2} + 4 \cdot 2 πn : 6 π + 8 πn

4 \cdot \frac{3 π}{2} + 4 \cdot 2 πn

4 \cdot \frac{3 π}{2} = 6 π

4 \cdot \frac{3 π}{2}

分式相乘:

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

= \frac{3 π 4}{2}

数字相乘:

3 \cdot 4 = 12

= \frac{12 π}{2}

数字相除:

\frac{12}{2} = 6

= 6 π

4 \cdot 2 πn = 8 πn

4 \cdot 2 πn

数字相乘:

4 \cdot 2 = 8

= 8 πn

= 6 π + 8 πn

4 x - π = 6 π + 8 πn

4 x - π = 6 π + 8 πn

4 x - π = 6 π + 8 πn

将

π

到右边

4 x - π = 6 π + 8 πn

两边加上

π

4 x - π + π = 6 π + 8 πn + π

化简

4 x = 7 π + 8 πn

4 x = 7 π + 8 πn

两边除以

4

4 x = 7 π + 8 πn

两边除以

4

\frac{4 x}{4} = \frac{7 π}{4} + \frac{8 πn}{4}

化简

x = \frac{7 π}{4} + 2 πn

x = \frac{7 π}{4} + 2 πn

x = \frac{7 π}{4} + 2 πn

作图

流行的例子

cot(θ)=(5.8473)

cot (θ) = (5.8473)

6=2+5arctan(x/2)

6 = 2 + 5 arctan (\frac{x}{2})

tan^2(θ)-2sec(θ)=2

tan^{2} (θ) - 2 sec (θ) = 2

-sin(B)-4=3sin(B)-5

- sin (B) - 4 = 3 sin (B) - 5

cos^2(x)-7cos(x)-1=0

cos^{2} (x) - 7 cos (x) - 1 = 0