---[Ratio of the areas of two triangles having equal heights is equal to the ratio of their corresponding base.]
iii. ∆QST and ∆RST lie between the same parallel lines ST and QR
\(\therefore\) Their heights are equal. Also ST is the common base.
\(\therefore\) A(∆QST) = A(∆RST) = 1
---[Areas of two triangles having common base and equal heights are equal.]
