sin x when x=7pi/12 use the sum Identity
sin (7pi /12) =
sin (pi/4 + pi/3) =
sin (pi/4) cos (pi/3) + sin(pi/3)cos(pi/4) =
√2/2 * 1/2 + √3/2 * √2/2 =
√2/4 + √6/4 =
[ √2 + √6 ] / 4