alleryIf sin θ = 3/5 (θ in Q1), find cos θ:
A3/4
B4/3
C5/3
D4/5
Answer & Solution
Correct answer: D. 4/5
Using sin²θ + cos²θ = 1: cos²θ = 1 - 9/25 = 16/25
→ cos θ = ±4/5. In Q1, cos > 0, so cos θ = 4/5. (Note: 3-4-5 right triangle.)
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