Question

2sinpi/8*cospi/5=?
Преобразование произведения в сумму

Answer 1

2sinpi/8*cospi/5 = 2(sinpi/8*cospi/5) =
2(1/2(sin(pi/8+pi/5) + sin(pi/8 - pi/5))) =
sin13pi/40 + sin(-3pi/40) =
sin13pi/40 - sin3pi/40