Упростите:
[tex]\frac{1}{1-tg^2\alpha}-\frac{1}{1-ctg^2\alpha}[/tex]
Правильный ответ [tex]\frac{1}{cos2\alpha}[/tex]
тогда
1/(1-tg²α)-1/(1-ctg²α)=cos²α/(cos²α-sin²α)-sin²α/(sin²α-cos²α)=(cos²α+sin²α)/(cos²α-sin²α)=1/cos2α.
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Verified answer
тогда
1/(1-tg²α)-1/(1-ctg²α)=cos²α/(cos²α-sin²α)-sin²α/(sin²α-cos²α)=(cos²α+sin²α)/(cos²α-sin²α)=1/cos2α.