E.5 ASSIGNMENT Rectangles geometry

What basic trigonometric identity would you use to verify that sin x cos x tan x =1-cos^(2)x?

Create a real-life situation and create a system and show how it might be modeled algebraically with a system of equations (or inequalities) show all work include a few sentences explaining the situation, your variables of choice and what each represents, and how you would set it up and solve it algebraically. !

Find the value of the variable and the length of each chord for #5 and #6.