- Let \(\triangle ABC\) be a triangle and a line \(DE \parallel BC\) intersecting \(AB\) at \(E\) and \(AC\) at \(F\). - By the basic proportionality theorem (Thales' theorem), we know that if a line is drawn parallel to one side of a triangle, it divides the other two sides proportionally.
\[ \frac{AE}{EB} = \frac{AF}{FC} \]
- This is the required proof.