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а)
![sin( alpha- beta)+2sin beta *cos alpha; \ alpha + beta = pi \ alpha = pi - beta \ sin( pi - 2beta )+2sin beta *cos( pi - beta) = sin2 beta -2sin beta *cos beta = \ =sin2 beta -sin2 beta =0 sin( alpha- beta)+2sin beta *cos alpha; \ alpha + beta = pi \ alpha = pi - beta \ sin( pi - 2beta )+2sin beta *cos( pi - beta) = sin2 beta -2sin beta *cos beta = \ =sin2 beta -sin2 beta =0](https://tex.z-dn.net/?f=sin%28+alpha-+beta%29%2B2sin+beta+%2Acos+alpha%3B+%5C+++alpha+%2B++beta++%3D++pi++%5C++++alpha+%3D+pi+-+beta++%5C+sin%28+pi+-++2beta++%29%2B2sin+beta+%2Acos%28+pi+-+beta%29++%3D+sin2+beta+-2sin+beta+%2Acos+beta+%3D++%5C+%3Dsin2+beta+-sin2+beta+%3D0)
б)
![alpha neq frac{ pi n}{2} \ \ cos^2 alpha + frac{sin( frac{ pi }{2}+ alpha )*cos( pi - alpha )}{ctg( pi - alpha )*tg( frac{3 pi }{2} - alpha )} = cos^2 alpha + frac{cos alpha *(-cos alpha )}{-ctg alpha *ctg alpha } = \ \ cos^2 alpha + frac{cos^2 alpha}{ctg^2 alpha } = cos^2 alpha(1+tg^2 alpha ) = cos^2 alpha* frac{1}{cos^2 alpha} = 1 alpha neq frac{ pi n}{2} \ \ cos^2 alpha + frac{sin( frac{ pi }{2}+ alpha )*cos( pi - alpha )}{ctg( pi - alpha )*tg( frac{3 pi }{2} - alpha )} = cos^2 alpha + frac{cos alpha *(-cos alpha )}{-ctg alpha *ctg alpha } = \ \ cos^2 alpha + frac{cos^2 alpha}{ctg^2 alpha } = cos^2 alpha(1+tg^2 alpha ) = cos^2 alpha* frac{1}{cos^2 alpha} = 1](https://tex.z-dn.net/?f=+alpha++neq++frac%7B+pi+n%7D%7B2%7D++%5C++%5C+cos%5E2+alpha+%2B++frac%7Bsin%28+frac%7B+pi+%7D%7B2%7D%2B+alpha++%29%2Acos%28+pi+-+alpha+%29%7D%7Bctg%28+pi+-+alpha+%29%2Atg%28+frac%7B3+pi+%7D%7B2%7D+-+alpha+%29%7D++%3D+cos%5E2+alpha+%2B++frac%7Bcos+alpha+%2A%28-cos+alpha+%29%7D%7B-ctg+alpha+%2Actg+alpha+%7D+%3D++%5C++%5C++cos%5E2+alpha+%2B++frac%7Bcos%5E2+alpha%7D%7Bctg%5E2+alpha+%7D++%3D+cos%5E2+alpha%281%2Btg%5E2+alpha+%29+%3D+cos%5E2+alpha%2A+frac%7B1%7D%7Bcos%5E2+alpha%7D++%3D+1)
б)
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