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受欢迎的三角函数 >

cot(b)=(tan(b)cot(b))/(csc(b))

解答

cot (b) = \frac{tan ( b ) cot ( b )}{csc ( b )}

解答

b = 0.90455 \dots + 2 πn, b = 2 π - 0.90455 \dots + 2 πn

+1

度数

b = 51.82729 \dots^{\circ} + 36 0^{\circ} n, b = 308.17270 \dots^{\circ} + 36 0^{\circ} n

求解步骤

cot (b) = \frac{tan ( b ) cot ( b )}{csc ( b )}

两边减去

\frac{tan ( b ) cot ( b )}{csc ( b )}

cot (b) - \frac{tan ( b ) cot ( b )}{csc ( b )} = 0

化简

cot (b) - \frac{tan ( b ) cot ( b )}{csc ( b )} : \frac{cot ( b ) csc ( b ) - tan ( b ) cot ( b )}{csc ( b )}

cot (b) - \frac{tan ( b ) cot ( b )}{csc ( b )}

将项转换为分式:

cot (b) = \frac{cot ( b ) csc ( b )}{csc ( b )}

= \frac{cot ( b ) csc ( b )}{csc ( b )} - \frac{tan ( b ) cot ( b )}{csc ( b )}

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{cot ( b ) csc ( b ) - tan ( b ) cot ( b )}{csc ( b )}

\frac{cot ( b ) csc ( b ) - tan ( b ) cot ( b )}{csc ( b )} = 0

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

cot (b) csc (b) - tan (b) cot (b) = 0

用 sin, cos 表示

\frac{cos ( b )}{sin ( b )} \cdot \frac{1}{sin ( b )} - \frac{sin ( b )}{cos ( b )} \cdot \frac{cos ( b )}{sin ( b )} = 0

化简

\frac{cos ( b )}{sin ( b )} \cdot \frac{1}{sin ( b )} - \frac{sin ( b )}{cos ( b )} \cdot \frac{cos ( b )}{sin ( b )} : \frac{cos ( b ) - sin ^{2} ( b )}{sin ^{2} ( b )}

\frac{cos ( b )}{sin ( b )} \cdot \frac{1}{sin ( b )} - \frac{sin ( b )}{cos ( b )} \cdot \frac{cos ( b )}{sin ( b )}

\frac{cos ( b )}{sin ( b )} \cdot \frac{1}{sin ( b )} = \frac{cos ( b )}{sin ^{2} ( b )}

\frac{cos ( b )}{sin ( b )} \cdot \frac{1}{sin ( b )}

分式相乘:

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

= \frac{cos ( b ) \cdot 1}{sin ( b ) sin ( b )}

乘以:

cos (b) \cdot 1 = cos (b)

= \frac{cos ( b )}{sin ( b ) sin ( b )}

sin (b) sin (b) = sin^{2} (b)

sin (b) sin (b)

使用指数法则:

a^{b} \cdot a^{c} = a^{b + c}

sin (b) sin (b) = sin^{1 + 1} (b)

= sin^{1 + 1} (b)

数字相加:

1 + 1 = 2

= sin^{2} (b)

= \frac{cos ( b )}{sin ^{2} ( b )}

\frac{sin ( b )}{cos ( b )} \cdot \frac{cos ( b )}{sin ( b )} = 1

\frac{sin ( b )}{cos ( b )} \cdot \frac{cos ( b )}{sin ( b )}

分式相乘:

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

= \frac{sin ( b ) cos ( b )}{cos ( b ) sin ( b )}

约分:

sin (b)

= \frac{cos ( b )}{cos ( b )}

约分:

cos (b)

= 1

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

将项转换为分式:

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

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

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{cos ( b ) - 1 \cdot sin ^{2} ( b )}{sin ^{2} ( b )}

乘以:

1 \cdot sin^{2} (b) = sin^{2} (b)

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

\frac{cos ( b ) - sin ^{2} ( b )}{sin ^{2} ( b )} = 0

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

cos (b) - sin^{2} (b) = 0

两边加上

sin^{2} (b)

cos (b) = sin^{2} (b)

两边进行平方

cos^{2} (b) = (sin^{2} (b))^{2}

两边减去

(sin^{2} (b))^{2}

cos^{2} (b) - sin^{4} (b) = 0

分解

cos^{2} (b) - sin^{4} (b) : (cos (b) + sin^{2} (b)) (cos (b) - sin^{2} (b))

cos^{2} (b) - sin^{4} (b)

使用指数法则:

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

sin^{4} (b) = (sin^{2} (b))^{2}

= cos^{2} (b) - (sin^{2} (b))^{2}

使用平方差公式:

x^{2} - y^{2} = (x + y) (x - y)

cos^{2} (b) - (sin^{2} (b))^{2} = (cos (b) + sin^{2} (b)) (cos (b) - sin^{2} (b))

= (cos (b) + sin^{2} (b)) (cos (b) - sin^{2} (b))

(cos (b) + sin^{2} (b)) (cos (b) - sin^{2} (b)) = 0

分别求解每个部分

cos (b) + sin^{2} (b) = 0 or cos (b) - sin^{2} (b) = 0

cos (b) + sin^{2} (b) = 0 : b = arccos (- \frac{- 1 + 5}{2}) + 2 πn, b = - arccos (- \frac{- 1 + 5}{2}) + 2 πn

cos (b) + sin^{2} (b) = 0

使用三角恒等式改写

cos (b) + sin^{2} (b)

使用毕达哥拉斯恒等式:

cos^{2} (x) + sin^{2} (x) = 1

sin^{2} (x) = 1 - cos^{2} (x)

= cos (b) + 1 - cos^{2} (b)

1 + cos (b) - cos^{2} (b) = 0

用替代法求解

1 + cos (b) - cos^{2} (b) = 0

令

: cos (b) = u

1 + u - u^{2} = 0

1 + u - u^{2} = 0 : u = - \frac{- 1 + 5}{2}, u = \frac{1 + 5}{2}

1 + u - u^{2} = 0

改写成标准形式

a x^{2} + b x + c = 0

- u^{2} + u + 1 = 0

使用求根公式求解

- u^{2} + u + 1 = 0

二次方程求根公式:

若

a = - 1, b = 1, c = 1

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

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

1^{2} - 4 (- 1) \cdot 1 = 5

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

使用法则

1^{a} = 1

1^{2} = 1

= 1 - 4 (- 1) \cdot 1

使用法则

- (- a) = a

= 1 + 4 \cdot 1 \cdot 1

数字相乘:

4 \cdot 1 \cdot 1 = 4

= 1 + 4

数字相加:

1 + 4 = 5

= 5

u_{1, 2} = \frac{- 1 \pm 5}{2 ( - 1 )}

将解分隔开

u_{1} = \frac{- 1 + 5}{2 ( - 1 )}, u_{2} = \frac{- 1 - 5}{2 ( - 1 )}

u = \frac{- 1 + 5}{2 ( - 1 )} : - \frac{- 1 + 5}{2}

\frac{- 1 + 5}{2 ( - 1 )}

去除括号:

(- a) = - a

= \frac{- 1 + 5}{- 2 \cdot 1}

数字相乘:

2 \cdot 1 = 2

= \frac{- 1 + 5}{- 2}

使用分式法则:

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

= - \frac{- 1 + 5}{2}

u = \frac{- 1 - 5}{2 ( - 1 )} : \frac{1 + 5}{2}

\frac{- 1 - 5}{2 ( - 1 )}

去除括号:

(- a) = - a

= \frac{- 1 - 5}{- 2 \cdot 1}

数字相乘:

2 \cdot 1 = 2

= \frac{- 1 - 5}{- 2}

使用分式法则:

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

- 1 - 5 = - (1 + 5)

= \frac{1 + 5}{2}

二次方程组的解是:

u = - \frac{- 1 + 5}{2}, u = \frac{1 + 5}{2}

u = cos (b)

代回

cos (b) = - \frac{- 1 + 5}{2}, cos (b) = \frac{1 + 5}{2}

cos (b) = - \frac{- 1 + 5}{2}, cos (b) = \frac{1 + 5}{2}

cos (b) = - \frac{- 1 + 5}{2} : b = arccos (- \frac{- 1 + 5}{2}) + 2 πn, b = - arccos (- \frac{- 1 + 5}{2}) + 2 πn

cos (b) = - \frac{- 1 + 5}{2}

使用反三角函数性质

cos (b) = - \frac{- 1 + 5}{2}

cos (b) = - \frac{- 1 + 5}{2}

的通解

cos (x) = - a \Rightarrow x = arccos (- a) + 2 πn, x = - arccos (- a) + 2 πn

b = arccos (- \frac{- 1 + 5}{2}) + 2 πn, b = - arccos (- \frac{- 1 + 5}{2}) + 2 πn

b = arccos (- \frac{- 1 + 5}{2}) + 2 πn, b = - arccos (- \frac{- 1 + 5}{2}) + 2 πn

cos (b) = \frac{1 + 5}{2} :

无解

cos (b) = \frac{1 + 5}{2}

- 1 \leq cos (x) \leq 1

无解

合并所有解

b = arccos (- \frac{- 1 + 5}{2}) + 2 πn, b = - arccos (- \frac{- 1 + 5}{2}) + 2 πn

cos (b) - sin^{2} (b) = 0 : b = arccos (\frac{- 1 + 5}{2}) + 2 πn, b = 2 π - arccos (\frac{- 1 + 5}{2}) + 2 πn

cos (b) - sin^{2} (b) = 0

使用三角恒等式改写

cos (b) - sin^{2} (b)

使用毕达哥拉斯恒等式:

cos^{2} (x) + sin^{2} (x) = 1

sin^{2} (x) = 1 - cos^{2} (x)

= cos (b) - (1 - cos^{2} (b))

- (1 - cos^{2} (b)) : - 1 + cos^{2} (b)

- (1 - cos^{2} (b))

打开括号

= - (1) - (- cos^{2} (b))

使用加减运算法则

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

= - 1 + cos^{2} (b)

= cos (b) - 1 + cos^{2} (b)

- 1 + cos (b) + cos^{2} (b) = 0

用替代法求解

- 1 + cos (b) + cos^{2} (b) = 0

令

: cos (b) = u

- 1 + u + u^{2} = 0

- 1 + u + u^{2} = 0 : u = \frac{- 1 + 5}{2}, u = \frac{- 1 - 5}{2}

- 1 + u + u^{2} = 0

改写成标准形式

a x^{2} + b x + c = 0

u^{2} + u - 1 = 0

使用求根公式求解

u^{2} + u - 1 = 0

二次方程求根公式:

若

a = 1, b = 1, c = - 1

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

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

1^{2} - 4 \cdot 1 \cdot (- 1) = 5

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

使用法则

1^{a} = 1

1^{2} = 1

= 1 - 4 \cdot 1 \cdot (- 1)

使用法则

- (- a) = a

= 1 + 4 \cdot 1 \cdot 1

数字相乘:

4 \cdot 1 \cdot 1 = 4

= 1 + 4

数字相加:

1 + 4 = 5

= 5

u_{1, 2} = \frac{- 1 \pm 5}{2 \cdot 1}

将解分隔开

u_{1} = \frac{- 1 + 5}{2 \cdot 1}, u_{2} = \frac{- 1 - 5}{2 \cdot 1}

u = \frac{- 1 + 5}{2 \cdot 1} : \frac{- 1 + 5}{2}

\frac{- 1 + 5}{2 \cdot 1}

数字相乘:

2 \cdot 1 = 2

= \frac{- 1 + 5}{2}

u = \frac{- 1 - 5}{2 \cdot 1} : \frac{- 1 - 5}{2}

\frac{- 1 - 5}{2 \cdot 1}

数字相乘:

2 \cdot 1 = 2

= \frac{- 1 - 5}{2}

二次方程组的解是:

u = \frac{- 1 + 5}{2}, u = \frac{- 1 - 5}{2}

u = cos (b)

代回

cos (b) = \frac{- 1 + 5}{2}, cos (b) = \frac{- 1 - 5}{2}

cos (b) = \frac{- 1 + 5}{2}, cos (b) = \frac{- 1 - 5}{2}

cos (b) = \frac{- 1 + 5}{2} : b = arccos (\frac{- 1 + 5}{2}) + 2 πn, b = 2 π - arccos (\frac{- 1 + 5}{2}) + 2 πn

cos (b) = \frac{- 1 + 5}{2}

使用反三角函数性质

cos (b) = \frac{- 1 + 5}{2}

cos (b) = \frac{- 1 + 5}{2}

的通解

cos (x) = a \Rightarrow x = arccos (a) + 2 πn, x = 2 π - arccos (a) + 2 πn

b = arccos (\frac{- 1 + 5}{2}) + 2 πn, b = 2 π - arccos (\frac{- 1 + 5}{2}) + 2 πn

b = arccos (\frac{- 1 + 5}{2}) + 2 πn, b = 2 π - arccos (\frac{- 1 + 5}{2}) + 2 πn

cos (b) = \frac{- 1 - 5}{2} :

无解

cos (b) = \frac{- 1 - 5}{2}

- 1 \leq cos (x) \leq 1

无解

合并所有解

b = arccos (\frac{- 1 + 5}{2}) + 2 πn, b = 2 π - arccos (\frac{- 1 + 5}{2}) + 2 πn

合并所有解

b = arccos (- \frac{- 1 + 5}{2}) + 2 πn, b = - arccos (- \frac{- 1 + 5}{2}) + 2 πn, b = arccos (\frac{- 1 + 5}{2}) + 2 πn, b = 2 π - arccos (\frac{- 1 + 5}{2}) + 2 πn

将解代入原方程进行验证

将它们代入

cot (b) = \frac{tan ( b ) cot ( b )}{csc ( b )}

检验解是否符合

去除与方程不符的解。

检验

arccos (- \frac{- 1 + 5}{2}) + 2 πn

的解:

假

arccos (- \frac{- 1 + 5}{2}) + 2 πn

代入

n = 1

arccos (- \frac{- 1 + 5}{2}) + 2 π 1

对于

cot (b) = \frac{tan ( b ) cot ( b )}{csc ( b )}

代入

b = arccos (- \frac{- 1 + 5}{2}) + 2 π 1

cot (arccos (- \frac{- 1 + 5}{2}) + 2 π 1) = \frac{tan ( arccos ( - \frac{- 1 + 5}{2} ) + 2 π 1 ) cot ( arccos ( - \frac{- 1 + 5}{2} ) + 2 π 1 )}{csc ( arccos ( - \frac{- 1 + 5}{2} ) + 2 π 1 )}

整理后得

- 0.78615 \dots = 0.78615 \dots

\Rightarrow 假

检验

- arccos (- \frac{- 1 + 5}{2}) + 2 πn

的解:

假

- arccos (- \frac{- 1 + 5}{2}) + 2 πn

代入

n = 1

- arccos (- \frac{- 1 + 5}{2}) + 2 π 1

对于

cot (b) = \frac{tan ( b ) cot ( b )}{csc ( b )}

代入

b = - arccos (- \frac{- 1 + 5}{2}) + 2 π 1

cot (- arccos (- \frac{- 1 + 5}{2}) + 2 π 1) = \frac{tan ( - arccos ( - \frac{- 1 + 5}{2} ) + 2 π 1 ) cot ( - arccos ( - \frac{- 1 + 5}{2} ) + 2 π 1 )}{csc ( - arccos ( - \frac{- 1 + 5}{2} ) + 2 π 1 )}

整理后得

0.78615 \dots = - 0.78615 \dots

\Rightarrow 假

检验

arccos (\frac{- 1 + 5}{2}) + 2 πn

的解:

真

arccos (\frac{- 1 + 5}{2}) + 2 πn

代入

n = 1

arccos (\frac{- 1 + 5}{2}) + 2 π 1

对于

cot (b) = \frac{tan ( b ) cot ( b )}{csc ( b )}

代入

b = arccos (\frac{- 1 + 5}{2}) + 2 π 1

cot (arccos (\frac{- 1 + 5}{2}) + 2 π 1) = \frac{tan ( arccos ( \frac{- 1 + 5}{2} ) + 2 π 1 ) cot ( arccos ( \frac{- 1 + 5}{2} ) + 2 π 1 )}{csc ( arccos ( \frac{- 1 + 5}{2} ) + 2 π 1 )}

整理后得

0.78615 \dots = 0.78615 \dots

\Rightarrow 真

检验

2 π - arccos (\frac{- 1 + 5}{2}) + 2 πn

的解:

真

2 π - arccos (\frac{- 1 + 5}{2}) + 2 πn

代入

n = 1

2 π - arccos (\frac{- 1 + 5}{2}) + 2 π 1

对于

cot (b) = \frac{tan ( b ) cot ( b )}{csc ( b )}

代入

b = 2 π - arccos (\frac{- 1 + 5}{2}) + 2 π 1

cot (2 π - arccos (\frac{- 1 + 5}{2}) + 2 π 1) = \frac{tan ( 2 π - arccos ( \frac{- 1 + 5}{2} ) + 2 π 1 ) cot ( 2 π - arccos ( \frac{- 1 + 5}{2} ) + 2 π 1 )}{csc ( 2 π - arccos ( \frac{- 1 + 5}{2} ) + 2 π 1 )}

整理后得

- 0.78615 \dots = - 0.78615 \dots

\Rightarrow 真

b = arccos (\frac{- 1 + 5}{2}) + 2 πn, b = 2 π - arccos (\frac{- 1 + 5}{2}) + 2 πn

以小数形式表示解

b = 0.90455 \dots + 2 πn, b = 2 π - 0.90455 \dots + 2 πn

作图

流行的例子

cos(x)+2sin(x)=-1

cos (x) + 2 sin (x) = - 1

csc (x) = - 7

cos(4t)+sin(4t)=0

cos (4 t) + sin (4 t) = 0

cos (x - 3 0^{\circ}) = 0.22

sin(4x-22)=cos(6x-13)

sin (4 x - 22) = cos (6 x - 13)