Rough diagram
Right triangle PQR where PQ = 4.5 cm, QR = 6 cm and PR = 7.5 cm.
Construction:
(i) Draw the ∆PQR with the given measurements.
(ii) Construct altitudes from any two vertices R and Q, to their opposite sides PQ and PR respectively.
(iii) The point of intersection of the altitude H is the orthocentre of the given ∆PQR.