已知xy+x+y=1,则arctanx+arctany等于
问题描述：
已知xy+x+y=1,则arctanx+arctany等于
答
另arctanx=a,arctany=b原式=a+btan(a+b)=sin(a+b)/cos(a+b)=(sinacosb+cosasinb)/(cosacosb-sinasinb)上下同除以cosacosb得tan(a+b)=(tana+tanb)/(1-tanatanb)将arctanx=a,arctany=b代入,tan(a+b)=(x+y)/(1-xy)由于x...