যদি tan (x - 30°) = 1/√3 হয়, তবে cosx = ?
Solution
Correct Answer: Option D
tan (x - 30°) = 1/√3
বা, tan (x - 30°) = tan 30°
বা, x - 30° = 30°
∴ x = 60°
∴ cosx = cos 60° = 1/2
বা, tan (x - 30°) = tan 30°
বা, x - 30° = 30°
∴ x = 60°
∴ cosx = cos 60° = 1/2
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