If (2cosA + 1)(2cosA - 1) = 0, 0° < A ≤ 90°, then find the value of A.
A. 90°
B. 45°
C. 30°
D. 60°
Answer: Option D
Solution(By Examveda Team)
(2cosA + 1)(2cosA - 1) = 0⇒ (2cosA)2 - (1)2 = 0
⇒ 4cos2A = 1
⇒ cos2A = $$\frac{1}{4}$$
⇒ cosA = $$\frac{1}{2}$$
⇒ cosA = cos60°
⇒ A = 60°
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