In □ABC, the line

Here AB, CD are parallel, then draw a line parallel to AB or CD through P.

Then,

We know that ,

Any three parallel lines will cut any two lines into pieces whose lengths are in the same ratio.

Therefore, if we consider QR, AP, line through B parallel to QR, then it divides the BA and BP in the same ratio.

----1

Similarly, if we consider QR,AP, line through B parallel to QR, then it divides the BA and BP in the same ratio.

--------2

From 1 & 2, we have,