[(tg^2(a)+1)cos^2(a)]/(1+tg(a)) + sin^2(a)/(1 - sin^2(a)) =
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(tg^2(a)+1)cos^2(a) = sin^2(a)cos^2(a)/cos^2(a) + cos^2(a) =
= sin^2(a) + cos^2(a) = 1
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sin^2(a)/(1 - sin^2(a)) = sin^2(a)/cos^2(a) = tg^2(a)
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= 1/(1+tg(a)) + tg^2(a)
a=45
tg(45)=1
1/(1+1) + 1^2 = 1,5