Math Problem Statement

Solve sin(x) = sin(-π/3) in the interval [0, 2π[.

Solution

To solve the equation sin(x)=sin(π3)\sin(x) = \sin\left(-\frac{\pi}{3}\right) in the interval [0,2π[[0, 2\pi[, follow these steps:

  1. Simplify the equation: Using the periodic and symmetry properties of the sine function, we know: sin(θ)=sin(θ).\sin(-\theta) = -\sin(\theta). Hence: sin(π3)=sin(π3)=32.\sin\left(-\frac{\pi}{3}\right) = -\sin\left(\frac{\pi}{3}\right) = -\frac{\sqrt{3}}{2}. Therefore, the equation becomes: sin(x)=32.\sin(x) = -\frac{\sqrt{3}}{2}.

  2. Find the general solutions: The sine function is negative in the third and fourth quadrants. The reference angle associated with 32-\frac{\sqrt{3}}{2} is: π3.\frac{\pi}{3}. Therefore, the solutions for xx in [0,2π[[0, 2\pi[ are: x=π+π3(third quadrant),x = \pi + \frac{\pi}{3} \quad \text{(third quadrant)}, and x=2ππ3(fourth quadrant).x = 2\pi - \frac{\pi}{3} \quad \text{(fourth quadrant)}.

  3. Simplify the solutions: x=π+π3=4π3,x = \pi + \frac{\pi}{3} = \frac{4\pi}{3}, and x=2ππ3=5π3.x = 2\pi - \frac{\pi}{3} = \frac{5\pi}{3}.

  4. Final solutions: The solutions to the equation in the interval [0,2π[[0, 2\pi[ are: x=4π3andx=5π3.x = \frac{4\pi}{3} \quad \text{and} \quad x = \frac{5\pi}{3}.

Would you like a detailed explanation of any of these steps or further help with similar problems?


Related Questions:

  1. How do the symmetry properties of trigonometric functions help in solving equations?
  2. What is the general solution for the equation sin(x)=k\sin(x) = k where kk is any constant?
  3. How can the periodicity of sine and cosine simplify solving trigonometric equations?
  4. How would the solutions change if the interval were different, e.g., [2π,2π][-2\pi, 2\pi]?
  5. How can you use a unit circle to find solutions for trigonometric equations?

Tip: Always sketch a unit circle to visualize the angles where trigonometric functions take specific values!

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Math Problem Analysis

Mathematical Concepts

Trigonometric Functions
Periodic Properties of Sine
Symmetry in Trigonometric Functions

Formulas

sin(-θ) = -sin(θ)
Solutions for sin(x) = k: x = arcsin(k) + 2nπ or x = π - arcsin(k) + 2nπ

Theorems

Symmetry of Trigonometric Functions
Periodicity of Sine

Suitable Grade Level

Grades 10-12