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受欢迎的三角函数 >

tan^2(θ)-3tan(θ)+2=0

解答

tan^{2} (θ) - 3 tan (θ) + 2 = 0

解答

θ = 1.10714 \dots + πn, θ = \frac{π}{4} + πn

+1

度数

θ = 63.43494 \dots^{\circ} + 18 0^{\circ} n, θ = 4 5^{\circ} + 18 0^{\circ} n

求解步骤

tan^{2} (θ) - 3 tan (θ) + 2 = 0

用替代法求解

tan^{2} (θ) - 3 tan (θ) + 2 = 0

令

: tan (θ) = u

u^{2} - 3 u + 2 = 0

u^{2} - 3 u + 2 = 0 : u = 2, u = 1

u^{2} - 3 u + 2 = 0

使用求根公式求解

u^{2} - 3 u + 2 = 0

二次方程求根公式:

若

a = 1, b = - 3, c = 2

u_{1, 2} = \frac{- ( - 3 ) \pm ( - 3 ) ^{2} - 4 \cdot 1 \cdot 2}{2 \cdot 1}

u_{1, 2} = \frac{- ( - 3 ) \pm ( - 3 ) ^{2} - 4 \cdot 1 \cdot 2}{2 \cdot 1}

(- 3)^{2} - 4 \cdot 1 \cdot 2 = 1

(- 3)^{2} - 4 \cdot 1 \cdot 2

使用指数法则:

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

若

n

是偶数

(- 3)^{2} = 3^{2}

= 3^{2} - 4 \cdot 1 \cdot 2

数字相乘:

4 \cdot 1 \cdot 2 = 8

= 3^{2} - 8

3^{2} = 9

= 9 - 8

数字相减:

9 - 8 = 1

= 1

使用法则

1 = 1

= 1

u_{1, 2} = \frac{- ( - 3 ) \pm 1}{2 \cdot 1}

将解分隔开

u_{1} = \frac{- ( - 3 ) + 1}{2 \cdot 1}, u_{2} = \frac{- ( - 3 ) - 1}{2 \cdot 1}

u = \frac{- ( - 3 ) + 1}{2 \cdot 1} : 2

\frac{- ( - 3 ) + 1}{2 \cdot 1}

使用法则

- (- a) = a

= \frac{3 + 1}{2 \cdot 1}

数字相加:

3 + 1 = 4

= \frac{4}{2 \cdot 1}

数字相乘:

2 \cdot 1 = 2

= \frac{4}{2}

数字相除:

\frac{4}{2} = 2

= 2

u = \frac{- ( - 3 ) - 1}{2 \cdot 1} : 1

\frac{- ( - 3 ) - 1}{2 \cdot 1}

使用法则

- (- a) = a

= \frac{3 - 1}{2 \cdot 1}

数字相减:

3 - 1 = 2

= \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

二次方程组的解是:

u = 2, u = 1

u = tan (θ)

代回

tan (θ) = 2, tan (θ) = 1

tan (θ) = 2, tan (θ) = 1

tan (θ) = 2 : θ = arctan (2) + πn

tan (θ) = 2

使用反三角函数性质

tan (θ) = 2

tan (θ) = 2

的通解

tan (x) = a \Rightarrow x = arctan (a) + πn

θ = arctan (2) + πn

θ = arctan (2) + πn

tan (θ) = 1 : θ = \frac{π}{4} + πn

tan (θ) = 1

tan (θ) = 1

的通解

tan (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} tan (x) 0 \frac{3}{3} 13 \pm \infty - 3 - 1 - \frac{3}{3}

θ = \frac{π}{4} + πn

θ = \frac{π}{4} + πn

合并所有解

θ = arctan (2) + πn, θ = \frac{π}{4} + πn

以小数形式表示解

θ = 1.10714 \dots + πn, θ = \frac{π}{4} + πn

作图

流行的例子

tan(θ)= 1/(sqrt(3))

tan (θ) = \frac{1}{3}

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

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

4sin(x)cos(x)=1

4 sin (x) cos (x) = 1

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

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

sin (x) = \frac{4}{5}