Question

prove that (1+tan²A) cos²A = 1
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Answer 1

Answer:

LHS = cos^2 a (1+ tan^2 a)

       = cos^2 a × sec^2 a             since (1+tan^2 a = sec^2 a)

       = cos^2 a × 1/ cos^2 a  

       = 1

       = RHS