For your reference
我想問,題目說座標「依序」題目的一下四個,為什麼(x,2x)不是C點,卻是設成D點
You can say that again
?
Not key point
I mean that the question said 4 spots set on the (x.y) should arrange counterclockwise. That is, ur pic was wrote D before C. C. should be wrote before D.
I had said you are right,your care is serious but it’s not key point.
我想知道為什麼不能用向量算?我的算式哪裡錯了
AD line can find out y=2x easily.