Take the kines you have graphed ....calculate the slope m....and show that no two lines have the same m
First of all...RICK doesn't form anything
I think it should be RKIC as shown below
Well anyway.....since two sides of a trapezoid must be parallel.....just show that the slopes between RK and KI and IC and CR are all unequal....and two of these must be equal to have a parallelogram