Ok I have these three points of the Cartesian plane (0,0),(2,3),(5,0)

And I have to find the area "inside these points" to me they look like a triangle

So I thought I would use 1/2 base(height)

perpendicular height for the base you choose
I used the distance formula to get the base from (0,0) to (5,0) as 5

I got height from from (2,3) to (0,0) as 5

this is not the perpendicular height for the chosen base
So I did (1/2)(5)(5)=12.5 only problem is that the answer in the back of my textbook says 15/2.