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受欢迎的三角函数 >

cot^2(3x)-2cot(3x)+1=0

解答

cot^{2} (3 x) - 2 cot (3 x) + 1 = 0

解答

x = \frac{π}{12} + \frac{πn}{3}

+1

度数

x = 1 5^{\circ} + 6 0^{\circ} n

求解步骤

cot^{2} (3 x) - 2 cot (3 x) + 1 = 0

用替代法求解

cot^{2} (3 x) - 2 cot (3 x) + 1 = 0

令

: cot (3 x) = u

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

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

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

使用求根公式求解

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

二次方程求根公式:

若

a = 1, b = - 2, c = 1

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

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

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

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

使用指数法则:

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

若

n

是偶数

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

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

数字相乘:

4 \cdot 1 \cdot 1 = 4

= 2^{2} - 4

2^{2} = 4

= 4 - 4

数字相减:

4 - 4 = 0

= 0

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

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

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

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

使用法则

- (- a) = a

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

数字相乘:

2 \cdot 1 = 2

= \frac{2}{2}

使用法则

\frac{a}{a} = 1

= 1

u = 1

二次方程组的解是:

u = 1

u = cot (3 x)

代回

cot (3 x) = 1

cot (3 x) = 1

cot (3 x) = 1 : x = \frac{π}{12} + \frac{πn}{3}

cot (3 x) = 1

cot (3 x) = 1

的通解

cot (x)

周期表（周期为

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} cot (x) \mp \infty 31 \frac{3}{3} 0 - \frac{3}{3} - 1 - 3

3 x = \frac{π}{4} + πn

3 x = \frac{π}{4} + πn

解

3 x = \frac{π}{4} + πn : x = \frac{π}{12} + \frac{πn}{3}

3 x = \frac{π}{4} + πn

两边除以

3

3 x = \frac{π}{4} + πn

两边除以

3

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

化简

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

化简

\frac{3 x}{3} : x

\frac{3 x}{3}

数字相除:

\frac{3}{3} = 1

= x

化简

\frac{\frac{π}{4}}{3} + \frac{πn}{3} : \frac{π}{12} + \frac{πn}{3}

\frac{\frac{π}{4}}{3} + \frac{πn}{3}

\frac{\frac{π}{4}}{3} = \frac{π}{12}

\frac{\frac{π}{4}}{3}

使用分式法则:

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

= \frac{π}{4 \cdot 3}

数字相乘:

4 \cdot 3 = 12

= \frac{π}{12}

= \frac{π}{12} + \frac{πn}{3}

x = \frac{π}{12} + \frac{πn}{3}

x = \frac{π}{12} + \frac{πn}{3}

x = \frac{π}{12} + \frac{πn}{3}

x = \frac{π}{12} + \frac{πn}{3}

合并所有解

x = \frac{π}{12} + \frac{πn}{3}

作图

流行的例子

-(tanh(nx))/(cosh(nx))=0

- \frac{tanh ( n x )}{cosh ( n x )} = 0

sin (φ) = 0

sin^2(x)=1-tan^2(x),0<= x<= pi/2

sin^{2} (x) = 1 - tan^{2} (x), 0 \leq x \leq \frac{π}{2}

sin (0.3 x) = 1

22.89 = cos (a)