1
cos70cos22-cos(90-22)sin(180-70)=cos70cos22-sin22sin70=cos(70+22)=
=cos92=cos(90+2)=-sin2<0<br>2
(1-cos(90+2a))/2-(1-cos(60-2a)/2-1/2*sin(15-15-2a)-1/2*sin(15+15+2a)=
=1/2+1/2*sin2a-1/2+1/2cos(60-2a)+1/2*sin2a-1/2sin(30+2a)=
=sin2a+1/2cos(60-2a)-1/2cos(60-2a)=sin2a
cos(60-2a)=sin(30+2a)