李小豹：sin15度乘以cos15度等于多少

风归云的回答：

sin15*cos15=1/2(2sin15*cos15)=1/2(sin30)=(1/2)*(1/2)=1/4

顾维的回答：

sin18*cos36 =sin18*cos368(2cos18)/(2cos18) =2sin18*cos18*cos36/(2cos18) =sin36*cos36/(2cos18) =(sin72 /2) / (2cos18) =sin72/(4cos18) =cos18/(4cos18) =1/4