lim sin7пx/sin8пx =|y=x-2, y->0|=lim sin7п(y+2)/sin8п(y+2)=
x->2
lim sin(7пy+14п)/sin(8пy+16п)=lim sin7пy/sin8пy=
y->0
=7/8*lim [(sin7пy /7пy) * (8пy/sin8пy)]=7/8*1*1=7/8

lim sinx/x = 1 - замечательный предел
x->0