Question

How to derive The following identities
A. 1 + cos^ A = 2 cos^A
B. 1 - cos^A = 2 sin^A
C. 1 + cosA = 2 cos^A/2
D. 1 - cosA = 2 sin^A/2
E. 1 + cos4A = 2 cos^A
F. sinA = (2 tanA/2)/(1+tan^A/2)
G. cosA = (1-tan^A/2)/(1+tan^A/2)

Answer 1

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