# Algebra II Terms

## Get down with the lingo

### Amplitude

How high can it go? Amplitude = max displacement.### Cofunction

*Co*mplementary functions. In a nutshell: cofunction A = function (A – 90°).

### Cosecant

When the sine function goes topsy-turvy. Reciprocal of the sine function or just the sine function flipped over. Also, it's the cofunction of secant.### Cosine

In a right triangle, cosine equals an angle's adjacent leg over the hypotenuse. Also, it's the cofunction of sine.### Cotangent

When the tangent function goes topsy-turvy. Reciprocal of the tangent function or just the tangent function flipped over. Also, it's the cofunction of tangent.### Hypotenuse

Looks a little like the word hippo, so remember hippos are big and the "hypos" are the biggest side of the right triangle. It's the side opposite the right angle in a right triangle.### Leg

They're kind of like people legs, but for triangles. They don't won't be caught dead in jeggings. Two legs hold the hypotenuse up. It's also a side opposite an acute angle in a right triangle.### Midline

The middle of the road—the horizontal line halfway between maximum and minimum displacement.### Period

This is how long it takes for one complete cycle. Up and down we go, where the sine function stops nobody knows.### Periodic Function

A function that repeats over and over—think sine and cosine.### Pythagorean Identity

This guy gets us to the unit circle, in all of its glory: sin^{2}ɵ + cos

^{2}ɵ = 1. It will come in handy for the rest of your math life. Learn to love it.

### Pythagorean Theorem

Thanks to our buddy Pythagoras, we can know all kinds of stuff about triangles using this theorem: a^{2}+ b

^{2}= c

^{2}. It's a way to find the leg or hypotenuse of a right triangle if the other two sides are known.

### Quadrant

Remember: "quad" means "4." So, a quadrant is just one fourth of coordinate plane. You see this word when talking about graphing on an*x*-

*y*plane, so it's not a totally new idea.