Use a half-angle formula to find the exact value of the following expression. cos 22.5 Determine an appropriate half-angle formula for cosine and the measure of the angle. Select the correct choice below and fill in the answer box to complete your choice. (Type an integer or a decimal.) O A. 1 - cos cos 22.5" = - 2 O B. 1+ cos cos 22.5" = 2 O C. 1 - cos cos 22.5" = 2 O D. 1 + cos cos 22.5* = - 2 cos 22.50 = (Simplify your answer, including any radicals. Use integers or fractions for any numbers in the expression. Rationalize the denominator.)