Question

前天帮上高一的弟弟做一道题做了好久没做出来,大汗,

Answer 1

5sinx=3sin(x-2y)

5sin(x-y+y)=3sin(x-y-y)

5sin(x-y)cosy+5cos(x-y)siny=3sin(x-y)cosy-3cos(x-y)siny

两边同除cos(x-y)cosy得

5tan(x-y)+5tany=3tan(x-y)-3tany

2tan(x-y)+8tany=0

所以

tan(x-y)+4tany=0