3sinα=cosα-16sinα/2 cosα/2 =2(cosα/2)^2-23sinα/2 cosα/2 =(cosα/2)^2-1两边除以(cosα/2)^23tanα/2=1- 1/(cosα/2)^23tan α/2=1- (sec α/2)^23tan α/2=1- 1-(tan α/2)^23tan α/2+(tan α/2)^2=0tan...