Question

( cos ^{2} 2 x=1-cos ^{2} 3 x )
( begin{array}{c}cos ^{2} 2 x=sin ^{2} 3 x cos ^{2} 2 x=cos ^{2}(pi / 2-3 x) 2 x=quad text { akn } pm(pi / 2-3 x) 5 x=operatorname{akt}+pi / 2 & x=(2 k+1) pi / 10end{array} )

# Q.13 Find the general solution of x, cos2 2x + cos2 3x = 1 (A) (2k + 1) + k € I (B) (nk + 1) o ; ke I (C) (3k – 1) , k € I (D) None of these

Solution