tan(a)=2tan(b)=3求a+btan(a+b)=(2+3)/(1-2x3)=-1a+b=arctan(-1)=派-arctan1
tan(x)=2 tan(y)=3 求x+ytan(x+y)=(2+3)/(1-2x3)=-1 x+y=arctan(-1)=-1/4∏