Question

cos^2 a tg^2 a + sin^2 a ctg^2 a
помогите решить

Answer 1

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Answer 2

$cos^2acdot tg^2a+sin^2acdot ctg^2a=cos^2acdot (frac{1}{cos^2a}-1)+sin^2acdot (frac{1}{sin^2a}-1)=\\=1-cos^2a+1-sin^2a=2-(cos^2a+sin^2a)=2-1=1\\\P.S.; ; ; boxed {1+tg^2a=frac{1}{cos^2a}; ; ,; ; 1+ctg^2a=frac{1}{sin^2a}}$