sin（x+π/6）的 =1/4sin（7π/6 +x）+ [cos（5π/6 -x）]^2=sin(π+π/6 +x）+[cos[π-(π/6+x)]^2=-sin(x+π/6) + [cos(x+π/6)]^2=-sin(x+π/6) + {[1-[sin(x+π/6)]^2}=-1/4+[1-(1/4)^2]=-1/4+1-1/16=11/16
