Let us show that

Let A → (7, 9)

B → (3, -7)

C → (-3, 3)

be the vertices of a triangle.

We know that distance between two points (x₁, y₁) and (x₂, y₂) is given by .

Using the above distance formula,

AB

BC

CA

Now, (BC)² + (CA)²

and (AB)²

We find that (BC)² + (CA)² = (AB)²

Hence the points (7, 9), (3, –7) and (–3, 3) are the vertices of a right angled triangle.