Question

Упростите (на картинке)

Answer 1

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Answer 2

$(1+tg ^{2} \alpha )*Cos ^{2}a-1= \frac{1}{Cos ^{2} \alpha } *Cos ^{2} \alpha -1= 1-1=0$

$\frac{1+tg ^{2} \alpha }{1+Ctg ^{2} \alpha } * \frac{1}{Cos ^{2} \alpha-1 } = \frac{ \frac{1}{Cos ^{2} \alpha } }{ \frac{1}{Sin ^{2} \alpha } } * \frac{1}{Cos ^{2} \alpha-1 } = -\frac{Sin ^{2} \alpha }{Cos ^{2} \alpha }* \frac{1}{Sin ^{2} \alpha }=- \frac{1}{Cos ^{2} \alpha }$