Use the cosine of a sum and cosine of a difference identities to find cos (s + t) and cos (s - t). cos s = 3/5 and sin t = - 2/5, s and t in quadrant IV cos (s + t) =
(Simplify your answer, including any radicals. Use integers or fractions for any numbers in the expression.) cos(s - t) = (Simplify your answer, including any radicals. Use integers or fractions for any numbers in the expression.)