Question

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Ctg a(((1+sin^2 a)/cos a ) - cos a)

Answer 1

$ctga((frac{1+sin^2a}{cosa})-cosa)=frac{cosa}{sina}((frac{cos^2a+sin^2a+sin^2a}{cosa})-cosa)=\=frac{cosa}{sina}(cosa+frac{2sin^2a}{cosa}-cosa)=frac{cosa}{sina}*frac{2sin^2a}{cosa}=2sina$