feunte tne Product as a Sum or difference b sin28x sin ilx S

feunte tne Product as a Sum or difference. b sin(28x) sin (ilx

Solution

sinAsinB=(1_/2)[cos(A-B)-cos(A+B)]

16sin(28x)sin(11x)=16(1_/2)[cos(28x-11x)-cos(28x+11x)]

=>16sin(28x)sin(11x)=8(cos(17x)-cos(39x))

=>16sin(28x)sin(11x)=8cos(17x)- 8cos(39x)