Y=tan(x+y）两边分别求对x的导数dy/dx＝d[tan(x+y)]/dx＝sec²(x+y)·d(x+y)/dx＝sec²(x+y)·(1+dy/dx)＝[1+tan²(x+y)]·(1+dy/dx)即：1+tan²(x+y)+tan²(x+y)·dy/dx＝0∴dy/dx＝-sec²...