Express the following as a multiplicative expression;

For example, for 1 - 2*cos^2(a), the answer would simplify to -1 * cos(2a):

1) sin(a - 2π/3) - sin(a + 2π/3)
2) sin(a + b) + sin(a - b)
3) cos(2a - π/16) + cos(9π/16 - 2a)