My purpose is (obviously) not to give you proofs so you won't have to do them yourself. Instead it's to show you good proof form. Do the proofs on your own, and then compare them to what I've done.
Chp 8. Right Triangles, How to Flatter Friends and Fluster Foes with Trigonometry
Chp 10. Area
Chp 11. Concurrency
Chp 12. Analytic Geometry