Construct an isosceles triangle ABC with sides AB = BC = 6 cm and ∠B = 80° and locate its orthocentre.

Rough Diagram:

Construction Steps:

Step 1: Draw the ΔABC with the given measurements.

Step 2: Construct altitudes from any two vertices (A and C) to their opposite sides (BC and AB) respectively.

The point of intersection of the altitudes H is the orthocenter of the given ΔABC.