Math Problem Statement

Solve

The angles α and β lie in the interval 0° < x < 180°, and are such that tan(α) = 2 tan(β) and tan(α + β) = 3. Find the possible values of α and β.

Solution

We are given two conditions involving angles α\alpha and β\beta within the interval 0<x<1800^\circ < x < 180^\circ:

  1. tanα=2tanβ\tan \alpha = 2 \tan \beta
  2. tan(α+β)=3\tan(\alpha + \beta) = 3

We need to find the possible values of α\alpha and β\beta.

Step 1: Use the tangent addition formula

The tangent of a sum is given by: tan(α+β)=tanα+tanβ1tanαtanβ\tan(\alpha + \beta) = \frac{\tan \alpha + \tan \beta}{1 - \tan \alpha \tan \beta} Substitute the known value tan(α+β)=3\tan(\alpha + \beta) = 3: 3=tanα+tanβ1tanαtanβ3 = \frac{\tan \alpha + \tan \beta}{1 - \tan \alpha \tan \beta} This equation will allow us to relate tanα\tan \alpha and tanβ\tan \beta.

Step 2: Use tanα=2tanβ\tan \alpha = 2 \tan \beta

From the first equation, tanα=2tanβ\tan \alpha = 2 \tan \beta. Let tanβ=t\tan \beta = t. Then, tanα=2t\tan \alpha = 2t.

Substitute these into the sum formula: 3=2t+t12tt3 = \frac{2t + t}{1 - 2t \cdot t} This simplifies to: 3=3t12t23 = \frac{3t}{1 - 2t^2}

Step 3: Solve for tt

Now solve the equation: 3(12t2)=3t3(1 - 2t^2) = 3t Expanding both sides: 36t2=3t3 - 6t^2 = 3t Rearrange it into a standard quadratic form: 6t2+3t3=06t^2 + 3t - 3 = 0 Simplify by dividing by 3: 2t2+t1=02t^2 + t - 1 = 0

Step 4: Solve the quadratic equation

We now solve 2t2+t1=02t^2 + t - 1 = 0 using the quadratic formula: t=1±124(2)(1)2(2)t = \frac{-1 \pm \sqrt{1^2 - 4(2)(-1)}}{2(2)} t=1±1+84t = \frac{-1 \pm \sqrt{1 + 8}}{4} t=1±94t = \frac{-1 \pm \sqrt{9}}{4} t=1±34t = \frac{-1 \pm 3}{4} Thus, t=24=12t = \frac{2}{4} = \frac{1}{2} or t=44=1t = \frac{-4}{4} = -1.

Step 5: Find tanα\tan \alpha and tanβ\tan \beta

We have two cases for tt:

  1. If t=12t = \frac{1}{2}, then tanβ=12\tan \beta = \frac{1}{2} and tanα=2×12=1\tan \alpha = 2 \times \frac{1}{2} = 1.
  2. If t=1t = -1, then tanβ=1\tan \beta = -1 and tanα=2×(1)=2\tan \alpha = 2 \times (-1) = -2.

Step 6: Find α\alpha and β\beta

Now, we find the angles corresponding to these tangent values:

  • For tanβ=12\tan \beta = \frac{1}{2} and tanα=1\tan \alpha = 1: β=tan1(12)26.57\beta = \tan^{-1}\left(\frac{1}{2}\right) \approx 26.57^\circ α=tan1(1)=45\alpha = \tan^{-1}(1) = 45^\circ

  • For tanβ=1\tan \beta = -1 and tanα=2\tan \alpha = -2: β=tan1(1)=135(since180>β>90)\beta = \tan^{-1}(-1) = 135^\circ \quad (\text{since} 180^\circ > \beta > 90^\circ) α=tan1(2)116.57\alpha = \tan^{-1}(-2) \approx 116.57^\circ

Final Solutions:

The possible values of α\alpha and β\beta are:

  1. α=45\alpha = 45^\circ, β=26.57\beta = 26.57^\circ
  2. α=116.57\alpha = 116.57^\circ, β=135\beta = 135^\circ

Would you like further clarification or more details on any step?

Here are 5 related questions for further exploration:

  1. What is the general solution for α\alpha and β\beta in terms of periodicity for tangent?
  2. How would the values change if the interval was extended beyond 0<x<1800^\circ < x < 180^\circ?
  3. How can we use trigonometric identities to verify the solutions obtained?
  4. Can you derive the tangent sum formula from the basic sine and cosine identities?
  5. What would happen if the given equations involved sine or cosine instead of tangent?

Tip: Remember that the tangent function repeats every 180°, so always consider possible periodic solutions in such trigonometric problems.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Tangent Function
Algebraic Manipulation
Quadratic Equations

Formulas

tan(α + β) = (tan(α) + tan(β)) / (1 - tan(α) tan(β))
Quadratic formula: x = (-b ± √(b² - 4ac)) / 2a

Theorems

Trigonometric Addition Formula
Quadratic Equation Theorem

Suitable Grade Level

Grades 10-12