Explain in a few sentences an outline of how you would use this figure to prove that abcd is a square

Logan wants to know how many skateboards have defective parts. he inspects 20,000 skateboards and keeps track of the number of defects per board. use his probability distribution table to find the expected value for defects on a skateboard.

Determine the solution for mc001-1.jpeg

Find the length of the normal and the angle it makes with the positive x-axis. (see pictured below)