(a-b).c+6
(-11-4).-4+6
-15.-4+6
60+6=66
1) S= v*t=2*t
2) S=5*t........................
<span>cos80*1/2(cos60-cos160)=cos80*1/2(1/2+cos20)=1/4cos80+1/2cos80cos20=
=1/4cos80+1/2*1/2(cos60+cos100)=1/4cos80+1/4*1/2+1/4cos100=
=1/4sin10+1/8-1/4sin10=1/8</span>