point N is(1/5,2/5) the area is 1/5
according to the normal at the points O(0,0) and A(0,1),we can get two line,they are y=2x and y=-1/2（x-1）,thus,we can get x=1/5,y=2/5,this is point N,so the area=1/2*2/5=1/5
OR you can tell your teacher ：i am chinese,this is so easy,N is(1/5,2/5) the area is 1/5题目什么意思 normal怎么用normal是法线