If the coordinates of a triangle ABC is A(3,1), B(5,1) and C(5,8) then find the side of the triangle which is parallel to the Y-axis.
BC
The sides for the triangle ABC are AB, BC, CA.
All the points with same X-coordinates form a line which is parallel to Y-axis. Among the given points B and C have the same Y-coordinates. So line BC will be parallel to Y-axis.