Math Problem Statement

Find the general solution of the equation cos θ = 1/2. Note: below n ∈ ℤ.

Solution

The equation you're working with is:

cosθ=12\cos \theta = \frac{1}{2}

General Solution:

To find the general solution for this equation, we first recognize that the cosine function has the value 12\frac{1}{2} at specific angles in the unit circle.

  • The angle θ=π3\theta = \frac{\pi}{3} (or 60°) satisfies the equation, since cos(π3)=12\cos \left( \frac{\pi}{3} \right) = \frac{1}{2}.
  • Additionally, cosine is positive in both the first and fourth quadrants. Therefore, the other solution in the range of one full rotation (0 to 2π2\pi) will be θ=2ππ3=5π3\theta = 2\pi - \frac{\pi}{3} = \frac{5\pi}{3}.

Thus, the general solutions are:

θ=π3+2nπorθ=5π3+2nπ\theta = \frac{\pi}{3} + 2n\pi \quad \text{or} \quad \theta = \frac{5\pi}{3} + 2n\pi

Where nZn \in \mathbb{Z}, indicating that the solutions repeat every full revolution of the unit circle (multiples of 2π2\pi).

Final General Solution:

θ=π3+2nπorθ=5π3+2nπ,nZ\theta = \frac{\pi}{3} + 2n\pi \quad \text{or} \quad \theta = \frac{5\pi}{3} + 2n\pi, \quad n \in \mathbb{Z}

Would you like further clarification or have other related questions?

Here are some related questions to explore:

  1. What are the solutions for other trigonometric functions like sine or tangent?
  2. How do periodicity and symmetry affect the general solution of trigonometric equations?
  3. How would the solution change if cosθ=12\cos \theta = -\frac{1}{2}?
  4. How do you graph the general solution of cosθ=12\cos \theta = \frac{1}{2}?
  5. How would you use the unit circle to solve trigonometric equations?

Tip: Remember, for periodic functions like cosine, adding multiples of the period (in this case, 2π2\pi) gives you the general solution.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
General Solutions of Trigonometric Equations
Unit Circle

Formulas

cos θ = ±cos α ⇒ θ = ±α + 2nπ (n ∈ ℤ)

Theorems

Periodic Nature of Cosine Function

Suitable Grade Level

Grades 11-12