# Trigonometry

# Sum and Difference of Angles Identities

In this "State of the Triangle" teaching address, President ObaMATH explores how to apply sum and difference identities with trigonometry. Trig sum and difference formulas help us evaluate sin, cos, tan, csc, sec, and cot of non special right triangle angles, like sin 15°, for example. Um, get ready to sing with us, seriously? Seriously. YAY MATH!