Math Problem Statement

5cos⁡(22.5°)sin⁡(22.5°)

Solution

We can solve the expression 5cos(22.5)sin(22.5)5 \cos(22.5^\circ) \sin(22.5^\circ) by utilizing a trigonometric identity. Specifically, the product of sine and cosine can be expressed as:

sin(2θ)=2sin(θ)cos(θ)\sin(2\theta) = 2 \sin(\theta) \cos(\theta)

Given that we have cos(22.5)sin(22.5)\cos(22.5^\circ) \sin(22.5^\circ), we can rewrite it as:

cos(22.5)sin(22.5)=12sin(45)\cos(22.5^\circ) \sin(22.5^\circ) = \frac{1}{2} \sin(45^\circ)

Since sin(45)=22\sin(45^\circ) = \frac{\sqrt{2}}{2}, we get:

cos(22.5)sin(22.5)=12×22=24\cos(22.5^\circ) \sin(22.5^\circ) = \frac{1}{2} \times \frac{\sqrt{2}}{2} = \frac{\sqrt{2}}{4}

Now, multiply this by 5:

5cos(22.5)sin(22.5)=5×24=5245 \cos(22.5^\circ) \sin(22.5^\circ) = 5 \times \frac{\sqrt{2}}{4} = \frac{5\sqrt{2}}{4}

Thus, the value of 5cos(22.5)sin(22.5)5 \cos(22.5^\circ) \sin(22.5^\circ) is 524\frac{5\sqrt{2}}{4}.

Would you like further details on this?

Here are some related questions:

  1. How do you prove the identity sin(2θ)=2sin(θ)cos(θ)\sin(2\theta) = 2 \sin(\theta) \cos(\theta)?
  2. What are the exact trigonometric values for other common angles, like 3030^\circ and 6060^\circ?
  3. Can you find the value of cos(45)\cos(45^\circ) and sin(45)\sin(45^\circ) using the unit circle?
  4. How do double-angle identities help in solving trigonometric equations?
  5. What are half-angle identities in trigonometry, and how can they be used?

Tip: Memorizing key trigonometric values like sin(45)\sin(45^\circ), cos(30)\cos(30^\circ), and their identities makes solving these expressions much faster!

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Angle Identities

Formulas

sin(2θ) = 2sin(θ)cos(θ)
cos(22.5°)sin(22.5°) = (1/2)sin(45°)

Theorems

Double-Angle Identity
Exact Trigonometric Values

Suitable Grade Level

Grades 10-12