3пsin(270) + 3пsin(a) + sin(270)sin(a) + sin(a)

= 3п(-1) + 3пsin(a) + (-1)sin(a) + sin(a)

= -3п + 3пsin(a) - sin(a) + sin(a)

= 3пsin(a) - sin(a)

= sin(a)(3п - 1)