Find the area of a triangle whose vertices have the coordinates (-1,7), (-1,2), (5,2).

Answer 1

There is a formula for the area given the co-ordinates, given by a determinant as follows:

(Note in this editor I cannot show the side bars on the determinant.

x₁ y₁ 1

x₂ y₂ 1

x₃ y₃ 1

If you do not know how to evaluate this determinant, I suggest you look it up.

Otherwise you can calculate the lengths of the sides of the triangle from the co-ordinates and then use Heron's formula, which you can also look up.