Use the half-angle identities to evaluate cos 22.5 exactly. . . . Which half-angle formula should be used to find the exact value of cos 22.5"? Select the correct choice below and fill in the answer boxes to complete your choice. (Do not include the degree symbol in your answers.) 1 - cos O A. cos 22.50 = cos 2 2 1 + cos O B. cos 22.5 = cos 2 2 1 + cos C. cos 22.50 = cos 2 2 1 - COS O D. cos 22.50 = cos 2 2