If sin(3x + 10º) = cos(2x - 5º), find x.
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Correct answer: D
Explanation
The correct answer is option 4 i.e. 17º.
sin(3x + 10°) = cos(2x − 5°)
cos A = sin(90° − A)
⇒ sin(3x + 10°) = sin(95° − 2x)
So,
3x + 10 = 95 − 2x
⇒ 5x = 85
⇒ x = 17°