Thanks to all of you who support me on Patreon. You da real mvps! $1 per month helps!! 🙂 https://www.patreon.com/patrickjmt !! Trigonometric Identities to Evaluate Expressions – Part 1 of 2 (Sum and Difference Identity) In this example I use a sum identity to evaluate sin(75 degrees) and tan (pi/12).