basic proportionality theorem
We can see a triangle ABD. m and m_1 are the slopes of the line segments BD and EC respectively. Observe that how the shape of the triangle gets changed when we move the points A, B, C. When point E is moved m_1 changes. We can change the value of CD using slide bar p.
Questions to think about AE, EB and AC are given so calculate the value of p such that AE/EB=AC/p and set the same value of p using the slide bar. What do we observe? For hint compare the values of m and m_1.