The ΔABC is made up of three lines, AB,BC and CA
For a right angle triangle, two lines must be at 90° so they are perpendicular to each other.
Checking for lines AB and BC
For two lines to be perpendicular, their product of slope must be equal to -1.
Given points A(1, 2), B(4, 5) and C(6, 3)
Checking slopes of line AB and BC
1×-1 = -1
So AB is Perpendicular to BC.
So it is a right angle triangle.