1.a) cos(70-10)=cos60=0.5
б)sin (35-5)=sin30=0.5
в) cos135= cos(90+45)=cos90*cos45-sin90*sin45=0*√2/2-1*√2/2=- √2/2
2. a) 4(cos²210-sin² 210)=4* cos(2*210)=4 cos420=4*cos (360+60)= 4*cos60=4*0.5=2
б) 2sin75*cos75=sin(2*75)=sin150=sin (180-30)=sin30=0.5