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1) (1-cos^2t)/1+cost=(1-cost)(1+cost)/1+cost=1-cost
2)(sin^2t+cos^2t)^2=1
3)((1-sin^2t)/1+sint)+sint=((1-sint)(1+sint)/1+sint)+sint=1-sint+sint=1
4)cos^2t(cos^2t+sin^2t)+sin^2t=cos^2t+sin^2t=1
5)cos^2t*sin^2t/cos^2t-sin^2tcos^2t=sin^2t-sin^2tcos^2t=
=sin^2t(1-cos^2t)=sin^2t*sin^2t=sin^4t
6)sin^2t+sin^2t=2sin^2t
7)cos^2t(tg^2t+1)=sin^2t+cos^2t=1
8)sin^2t(ctg^2t+1)=cos^2t+sin^2t=1
9)cos^2t
10)cos^2t-sin^2t-cos^2t= -sin^2t