Ответы и объяснения

2013-12-09T05:47:28+00:00
Cos^2(a)/sin^2(a)-cos^2(a)=ctg^2(a)*cos^2(a)
(cos^2(a)*(1-sin^2(a)))/sin^2(a)= ctg^2(a)*cos^2(a)
ctg^2(a)*(1-sin^2(a))=ctg^2(a)*cos^2(a)
ctg^2(a)*cos^2(a)= ctg^2(a)*cos^2(a)