If sin x = cos(2x + 15°), what is the value of x?
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Correct answer: C
Explanation
sin x = cos(2x + 15°)
According to the formula:
cosθ = sin(90° − θ)
sin x = sin(90° − (2x + 15°))
= sin(75° − 2x)
⇒ x = 75° − 2x
⇒ 3x = 75°
⇒ x = 25°