Answer :
use the identity cos^2 (a/2) = 1/2 (1 + cos a) so
cos^ 2 22.5 = cos^2 (45/2) = 1/2 ( 1 + cos 45) = 1/2(1 + sqrt2/ 2)4 = 1/2 + sqrt2/4
cos 22.5 = sqrt ( 1/2 + sqrt2/4) Answer
cos^ 2 22.5 = cos^2 (45/2) = 1/2 ( 1 + cos 45) = 1/2(1 + sqrt2/ 2)4 = 1/2 + sqrt2/4
cos 22.5 = sqrt ( 1/2 + sqrt2/4) Answer