Geometry is not my strong suit and Im struggling with a problem I've been assigned.
I'm relatively familiar with proving the cosine rule, however I cant seem to complete part a of the question which is used in the steps of part b.
I started showing that angle AED and angle BEC are similar due to being vertically opposite, however, should i be also trying to determine side lengths to prove similarity between both these triangles as I am struggling to find any other aspects that show these triangles are similar.
Any help would be much appreciated, Thanks. (Question is attached)
Question :
