Sup everyone! Anyone up for some jolly conversation?

The sum of two numbers is 86, and their difference is 20. find the two numbers

Me, prove a quadrilateral with vertices g(1,-1), h(5,1), i(4,3) and j(0,1) is a rectangle using the parallelogram method and a rectangle method.

Express the following as a function of a single angle. cos(60) cos(-20) - sin(60) sin(-20)