If $(2 \cos A+1)(2 \cos A-1)=0,0^{\circ}<A \leq 90^{\circ}$, then find the value of A.

90° 45° 30° 60°

60°

( 2cosA - 1 ) ( 2cosA + 1 ) = 0 4cos2A - 1 = 0 cos2A = \(\frac{1}{4}\)  cosA = \(\frac{1}{2}\)  & we know , cos60º = \(\frac{1}{2}\) So , A = 60º