If BM and CN are the perpendiculars drawn on the sides AC and AB of the triangle ABC, prove that the points B, C, M and N are concyclic.
Given: In DABC, MB AC and CN AB.
To Prove: Points B, C, M and N are Concyclic (lie on the same circle)
Proof:
Assume, BC is the diameter of a circle.
So BC will subtend an angle of 90° at any point on the circle.
Now, MB AC and CN AB. So these angles lie on the circle and the points N and M lie on this circle.
Hence, BCMN is concyclic.
Hence Proved.