5cos(x-y/2)+7cos(y/2)=0求tan(x/2)*tan[(x-y)/2]

Question

5cos(x-y/2)+7cos(y/2)=0求tan(x/2)*tan[(x-y)/2]

Answer 1

用积化和差做,可以得到5cos(x/2)*cos(x-y)/2=-cos(y/2),将tg化成sin/cos的形式,将[sin(x/2)*sin(x-y)/2]/-cos(y/2),将sin(x/2)*sin(x-y)/2]化成cos的形式(积化和差)可以最后算得答案为-6即是答案