tanX,tanY是方程X²+(4M+1)X+2M=0的俩根,且M≠-1/2求sin(X+Y)/cos(X-Y)
问题描述:
tanX,tanY是方程X²+(4M+1)X+2M=0的俩根,且M≠-1/2求sin(X+Y)/cos(X-Y)
答
sin(X+Y)/cos(X-Y)=(tanx+tany)/(1+tanxtany)
由于tanx,tany为方程X²+(4M+1)X+2M=0的俩根
所以,tanx+tany=-(4M+1),tanxtany=2M
所以sin(X+Y)/cos(X-Y)=(tanx+tany)/(1+tanxtany)=-(4M+1)/(2M+1)