Solve the equation 3sin(θ) - cos(θ) = 1 for 0° ≤ θ ≤ 360°.

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Understand the Problem

The question involves solving the trigonometric equation 3sin(θ) - cos(θ) = 1 within the interval 0° ≤ θ ≤ 360°. Key concepts include trigonometric identities and solving for the angle θ.

Answer

The solutions are $\theta = 0°, 36.87°, 143.13°, 180°$.
Answer for screen readers

The solutions to the equation $3 \sin \theta - \cos \theta = 1$ for $0° \leq \theta \leq 360°$ are: $$ \theta = 0°, 36.87°, 143.13°, 180° $$

Steps to Solve

  1. Rearranging the Equation

Start by rearranging the equation to isolate the trigonometric functions: $$ 3\sin \theta - \cos \theta = 1 \implies 3\sin \theta = \cos \theta + 1 $$

  1. Expressing in Terms of $\sin \theta$

Next, express $\cos \theta$ in terms of $\sin \theta$. Use the Pythagorean identity: $$ \cos^2 \theta = 1 - \sin^2 \theta \implies \cos \theta = \sqrt{1 - \sin^2 \theta} $$

  1. Substituting and Squaring

Substitute this expression back into the equation: $$ 3\sin \theta = \sqrt{1 - \sin^2 \theta} + 1 $$ Square both sides to eliminate the square root: $$ (3\sin \theta - 1)^2 = 1 - \sin^2 \theta $$

  1. Expanding the Equation

Expand the left side: $$ (3\sin \theta)^2 - 2(3\sin \theta)(1) + 1 = 1 - \sin^2 \theta $$ This gives: $$ 9\sin^2 \theta - 6\sin \theta + 1 = 1 - \sin^2 \theta $$

  1. Combining and Rearranging

Combine like terms to form a standard quadratic equation: $$ 9\sin^2 \theta + \sin^2 \theta - 6\sin \theta = 0 $$ This simplifies to: $$ 10\sin^2 \theta - 6\sin \theta = 0 $$

  1. Factoring the Equation

Factor out the common term: $$ 2\sin \theta(5\sin \theta - 3) = 0 $$ This gives the solutions: $$ \sin \theta = 0 \quad \text{or} \quad \sin \theta = \frac{3}{5} $$

  1. Finding Angles Corresponding to $\sin \theta = 0$

The angles where $\sin \theta = 0$ in the interval $[0°, 360°]$ are: $$ \theta = 0°, 180° $$

  1. Finding Angles Corresponding to $\sin \theta = \frac{3}{5}$

For $\sin \theta = \frac{3}{5}$, use the arcsine function: $$ \theta = \arcsin\left(\frac{3}{5}\right) \approx 36.87° $$ The sine function is positive in the first and second quadrants, giving: $$ \theta \approx 36.87°, 180° - 36.87° \approx 143.13° $$

  1. Listing All Solutions

The final solutions for the equation $3\sin \theta - \cos \theta = 1$ in the interval $[0°, 360°]$ are: $$ \theta \approx 0°, 36.87°, 143.13°, 180° $$

The solutions to the equation $3 \sin \theta - \cos \theta = 1$ for $0° \leq \theta \leq 360°$ are: $$ \theta = 0°, 36.87°, 143.13°, 180° $$

More Information

These angles correspond to specific positions on the unit circle, where the sine and cosine values align with the given equation. The solutions involve both exact values and approximate calculations.

Tips

  • Ignoring Quadrants: Failing to consider that sine values can be positive in both the first and second quadrants can lead to missing solutions.
  • Not Squaring Carefully: When squaring both sides of the equation, ensure that extraneous solutions are checked against the original equation.

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