Another Popular Trig Identity

Move the LARGE COLORED POINT anywhere you want on the horizontal axis. Then slide the slider slowly & observe what happens.

Express the area of the top rectangle in terms of θ.

What is the area of the bottom (empty) rectangle in terms of θ? How do you know this even though one of its sides wasn't labeled?

What is true about the area of the top colored rectangle and bottom rectangle?

Write a new trig identity (in terms of θ) that expresses the relationship you saw above.