In geometry, we learned about triangles, circles, and all of the other shapes in which we can cut pizza and crust-less PB & J. In Algebra II, we'll be re-introduced to trigonometric functions ("trig" functions for short). You've probably spotted these before, and possibly blocked them from your mind: Sine (sin), Cosine (cos), Tangent (tan), and all of their inverses. Trig functions are useful for finding angles, or using known angles to find length. Knowing these will be especially handy once we get around to learning Pre-calculus.