S(5) = 5/5+9,6 = 1 + 9,6 = 10,6...
A1=-10
a3=5
a2-?
a3=a1+2d=2d-10
a3=2d-10
5=2d-10
15=2d
d=7.5
a2=a1+d=-10+7.5=-2.5
((с+2√d)²/10(c+2√d)(c-2√d))((c-2√d)/(c+2√d))=((с+2√d)²(c-2√d))/(10(c-2√d)(c+2√d)²)=
1/10
Sin83cos67+cos83sin67=sin(83+67)=sin150=sin(180-30)=sin30=0.5