3sin52°30×sin7°30
..........................

sin(a)*sin(b) = 1/2(cos(a-b) - cos(a+b))3*(1/2(cos45- cos60))= 3* (1/2(√2/2 - 1/2))= 1,5(√2/2-1/2)= ((√2-1)*3)/4 = (3√2-3)/4