Question

What type of triangle is formed by joining the points D(7, 3), E(8, 1), and

Answer 1

D(7, 3), E(8, 1), and  F(4, -1)

We calculate the squared distances between the points:

$DE^2 = 1^2 + 2^2 = 5$

$EF^2=4^2+2^2=20$

$DF^2=3^2+4^2=25$

Since $DF^2=DE^2+EF^2$ we have a right triangle with hypotenuse DF.