Math Problem Statement

Solve the equation: sec^2(θ) + 3csc^2(θ) = 8

Solution

The equation in the image is:

sec2θ+3csc2θ=8\sec^2 \theta + 3 \csc^2 \theta = 8

Let’s solve for θ\theta.

Step 1: Recall the basic trigonometric identities.

  • sec2θ=1+tan2θ\sec^2 \theta = 1 + \tan^2 \theta
  • csc2θ=1+cot2θ\csc^2 \theta = 1 + \cot^2 \theta

These identities can be substituted into the equation to simplify.

Step 2: Substituting the identities

(1+tan2θ)+3(1+cot2θ)=8(1 + \tan^2 \theta) + 3(1 + \cot^2 \theta) = 8

Step 3: Expand the equation

1+tan2θ+3+3cot2θ=81 + \tan^2 \theta + 3 + 3 \cot^2 \theta = 8 tan2θ+3cot2θ+4=8\tan^2 \theta + 3 \cot^2 \theta + 4 = 8

Step 4: Simplify the equation

tan2θ+3cot2θ=4\tan^2 \theta + 3 \cot^2 \theta = 4

Step 5: Express cot2θ\cot^2 \theta in terms of tan2θ\tan^2 \theta

We know that: cot2θ=1tan2θ\cot^2 \theta = \frac{1}{\tan^2 \theta}

So, the equation becomes: tan2θ+3tan2θ=4\tan^2 \theta + \frac{3}{\tan^2 \theta} = 4

Step 6: Multiply the equation by tan2θ\tan^2 \theta to eliminate the denominator

Let x=tan2θx = \tan^2 \theta. Then, we get: x2+3=4xx^2 + 3 = 4x x24x+3=0x^2 - 4x + 3 = 0

Step 7: Solve the quadratic equation

(x3)(x1)=0(x - 3)(x - 1) = 0 Thus, x=3x = 3 or x=1x = 1.

Step 8: Solve for θ\theta

Since x=tan2θx = \tan^2 \theta, we have two cases:

  • If tan2θ=3\tan^2 \theta = 3, then tanθ=3\tan \theta = \sqrt{3}, which gives θ=60\theta = 60^\circ or θ=240\theta = 240^\circ.
  • If tan2θ=1\tan^2 \theta = 1, then tanθ=1\tan \theta = 1, which gives θ=45\theta = 45^\circ or θ=225\theta = 225^\circ.

Thus, the possible values of θ\theta are 4545^\circ, 6060^\circ, 225225^\circ, or 240240^\circ.


Would you like more details or clarifications?

Here are 5 related questions:

  1. What is the general solution for tanθ=1\tan \theta = 1?
  2. How would the equation change if the constant on the right-hand side were different?
  3. Can you solve this equation graphically using trigonometric curves?
  4. What other identities might help simplify equations involving sec2θ\sec^2 \theta and csc2θ\csc^2 \theta?
  5. How can you verify the solutions of a trigonometric equation using a calculator?

Tip: Always remember to check if your solutions lie within the required domain when solving trigonometric equations.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Quadratic Equations
Trigonometric Identities

Formulas

sec^2 θ = 1 + tan^2 θ
csc^2 θ = 1 + cot^2 θ
Quadratic equation: ax^2 + bx + c = 0

Theorems

Pythagorean identities
Quadratic formula

Suitable Grade Level

Grade 10-12