Draw an acute-angled ∆PQR. Draw all of its altitudes. Name the point of concurrence as ‘O’.

To draw altitudes of a triangle:

i. Draw an acute-angled ∆PQR.

ii. Draw a perpendicular from vertex P on the side QR using a set - square. Name the point where it meets side QR as M. Seg PM is an altitude on side QR.

iii. Considering side PR as a base, draw an altitude QX on side XZ. Seg QX is an altitude on side PR.

iv. Consider side PQ as a base, draw an altitude RN on seg PQ. Seg RN is an altitude on side PQ.

Hence,

Seg PM, seg QO, seg RN are the altitudes of ∆PQR. The point of concurrence i.e., the orthocentre is denoted by the point O.