Math Problem Statement

Solve the trigonometric inequality: sin(2x + π/6) ≤ 1/2.

Solution

The problem in the image involves solving the trigonometric inequality:

sin(2x+π6)12.\sin\left(2x + \frac{\pi}{6}\right) \leq \frac{1}{2}.

Step-by-Step Solution:

  1. Recall the Range of Sine: The sine function ranges from 1-1 to 11. Thus, this inequality is valid, as 12\frac{1}{2} lies within this range.

  2. Solve the Equality sin(2x+π6)=12\sin\left(2x + \frac{\pi}{6}\right) = \frac{1}{2}: The sine function equals 12\frac{1}{2} at two angles within one period (2π2\pi): α1=π6,α2=ππ6=5π6.\alpha_1 = \frac{\pi}{6}, \quad \alpha_2 = \pi - \frac{\pi}{6} = \frac{5\pi}{6}.

    Hence, we have: 2x+π6=π6+2nπor2x+π6=5π6+2nπ,2x + \frac{\pi}{6} = \frac{\pi}{6} + 2n\pi \quad \text{or} \quad 2x + \frac{\pi}{6} = \frac{5\pi}{6} + 2n\pi, where nZn \in \mathbb{Z} (integer).

  3. Solve for xx for Equality: Rearrange each equation for xx: 2x=π6π6+2nπx=nπ,2x = \frac{\pi}{6} - \frac{\pi}{6} + 2n\pi \quad \Rightarrow \quad x = n\pi, and 2x=5π6π6+2nπx=2π3+nπ.2x = \frac{5\pi}{6} - \frac{\pi}{6} + 2n\pi \quad \Rightarrow \quad x = \frac{2\pi}{3} + n\pi.

    Therefore, the solutions to the equality are: x=nπandx=2π3+nπ.x = n\pi \quad \text{and} \quad x = \frac{2\pi}{3} + n\pi.

  4. Solve the Inequality: The inequality sin(2x+π6)12\sin\left(2x + \frac{\pi}{6}\right) \leq \frac{1}{2} holds between these equality points: 2x+π6[π6,5π6].2x + \frac{\pi}{6} \in [\frac{\pi}{6}, \frac{5\pi}{6}].

    From here: [ 2x \in [0, \frac{2\pi}{3}] \quad \Rightarrow \quad x \in [0, \frac{\pi}{3}]. ]

  5. Generalize the Solution: Since sine is periodic with period 2π2\pi, repeat the intervals for all nZn \in \mathbb{Z}: xnZ[nπ,nπ+π3].x \in \bigcup_{n \in \mathbb{Z}} \left[n\pi, n\pi + \frac{\pi}{3}\right].

Final Answer:

The solution is: xnZ[nπ,nπ+π3].x \in \bigcup_{n \in \mathbb{Z}} \left[n\pi, n\pi + \frac{\pi}{3}\right].

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5 Related Questions:

  1. How do we solve trigonometric inequalities involving cosine instead of sine?
  2. What are the general solutions for sin(x)=c\sin(x) = c and cos(x)=c\cos(x) = c for given values of cc?
  3. How does the periodicity of trigonometric functions influence inequality solutions?
  4. What changes when solving sin(2x+a)12\sin(2x + a) \geq \frac{1}{2}?
  5. How can this solution be visualized graphically for better understanding?

Tip:

Always consider the periodicity of trigonometric functions to generalize solutions effectively when solving equations or inequalities!

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Inequalities
Periodic Functions

Formulas

General solution of sin(x) = c: x = arcsin(c) + 2nπ and x = π - arcsin(c) + 2nπ

Theorems

Periodicity of the sine function
Basic properties of sine and cosine

Suitable Grade Level

Grades 9-12