cos(3pi/2+a)sin(p+a)-tg(pi\2+a)tg(2pi+a)=>
cos(3pi/2+a)=sin a
sin(p+a)=-sin a
tg(pi\2+a)=-ctg a
tg(2pi+a)=tg a
(sin a)(-sin a)-(-ctg a)(tg a)= -sin^{2}a +1=cos^{2}a
cos(3pi/2+a)=sin a
sin(p+a)=-sin a
tg(pi\2+a)=-ctg a
tg(2pi+a)=tg a
(sin a)(-sin a)-(-ctg a)(tg a)= -sin^{2}a +1=cos^{2}a