A) cos2a cosa^2-sina^2 (cosa-sina)(cosa+sina)
_________ = _____________ = ___________________ = cosa+sina
cosa-sina cosa-sina cosa-sina
б) a a
cos^2_ -sina^2_
cosa 2 2 a a
__________ = ________________ = cos_+sin_
a a a a 2 2
cos_ - sin_ cos_ -sin_
2 2 2 2
a a
в) 4sin_ sin(90- _ ) sin(270-a)=-2sina cosa=-sin2a
2 2
г) sin^2a ctga sinacosa 1
__________ = _________ = __
sin2a 2sinacosa 2