We can prove this by using similar triangles. We know that angle ABE and ACD are SIMILAR(we know that by the sign in between them).Therefore, we also know that CDA and BEA are similar, and EAB and DAC are similar. Since all the angles are similar, we also know that the side lengths are equal in proportion. AB/AE is equal to AC/AD. When assigned values, that would create a proportion that is equal since the smaller triangle is similar to the bigger one. If you want to create a proof, break each statement into its own section.
