alleryIf cos x = -3/5 and x lies in the THIRD quadrant, then sin x equals:
A-4/5
B+3/4
C-3/4
D+4/5
Answer & Solution
Correct answer: A. -4/5
We have sin²x = 1 - cos²x.
That is sin²x = 1 - 9/25.
So sin²x = 16/25.
→ sin x = ±4/5. In Quadrant III, sin x is negative, so sin x = -4/5.
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