Mark M. answered 04/05/22
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Retired Math prof with teaching and tutoring experience in trig.
csc2a + sec2a = 1/sin2a + 1/cos2a = (cos2a + sin2a) / (sin2acos2a) = 1 / [(sin2a)(cos2a)] =
(1/sin2a)(1/cos2a) = (csc2a)(sec2a)