Math Problem Statement

In the xy-plane below, the terminal side of the angle θ lies so that 180° < θ < 270°. Find the value of sin 2θ.

Solution

To solve this problem, let’s go through the steps carefully.

Problem Analysis

We are given:

  • The terminal side of the angle θ\theta in the third quadrant (since 180<θ<270180^\circ < \theta < 270^\circ), with the coordinates (4,3)(-4, -3) as a point on the terminal side.
  • We are asked to find the value of sin2θ\sin 2\theta.

Steps to Solution

  1. Find rr (the radius or hypotenuse): r=x2+y2=(4)2+(3)2=16+9=25=5r = \sqrt{x^2 + y^2} = \sqrt{(-4)^2 + (-3)^2} = \sqrt{16 + 9} = \sqrt{25} = 5

  2. Determine sinθ\sin \theta and cosθ\cos \theta:

    • Since sinθ=yr\sin \theta = \frac{y}{r} and cosθ=xr\cos \theta = \frac{x}{r}, sinθ=35andcosθ=45\sin \theta = \frac{-3}{5} \quad \text{and} \quad \cos \theta = \frac{-4}{5}
  3. Use the Double-Angle Formula for Sine: sin2θ=2sinθcosθ\sin 2\theta = 2 \sin \theta \cos \theta Substituting the values we found: sin2θ=23545=21225=2425\sin 2\theta = 2 \cdot \frac{-3}{5} \cdot \frac{-4}{5} = 2 \cdot \frac{12}{25} = \frac{24}{25}

Answer

The value of sin2θ\sin 2\theta is 2425\frac{24}{25}, which matches option B.

Would you like further clarification on any of these steps or additional details?

Here are some related questions you might explore:

  1. How would we find cos2θ\cos 2\theta given the same information?
  2. What is the value of tan2θ\tan 2\theta for the same angle?
  3. Can we generalize this approach for any point in the third quadrant?
  4. How does the double-angle identity for sine differ from other double-angle identities?
  5. Why do the values of sinθ\sin \theta and cosθ\cos \theta have different signs in different quadrants?

Tip: Double-angle identities are useful in trigonometry when you know sinθ\sin \theta or cosθ\cos \theta but need to find expressions involving 2θ2\theta.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Trigonometry
Double-Angle Identities
Sine and Cosine Ratios

Formulas

Double-Angle Formula for Sine: sin 2θ = 2 sin θ cos θ
Distance Formula to find radius: r = √(x² + y²)

Theorems

Trigonometric Double-Angle Identity

Suitable Grade Level

Grades 10-12