# Gus and Lyle's Precalculus Website

## Glossary

### a

absolute value - The actual value of a number, without regard to its sign. **Ex.** The absolute value of -5 is 5. This is written as |5| = 5.

### c

complex number - A combination of a real number and an imaginary number, expressed in the form **a + bi**. **Ex.** 3 + 2𝑖

constant - A value that does not change in an algebraic equation. **Ex.** The 5 in 2x + 5 is a constant.

### e

ellipse - The set of all points (x,y) in a plane, the some of whose distances from two distinct fixed points (foci) is constant.

### f

function - A process in which each x value has a single corresponding y value. This can be confirmed on a graph using the vertical line test.

### h

hyperbola - The set of all points (x,y) in a plane, the difference of whose distances from two fixed points (foci) is a positive constant.

### l

line - A straight, one dimensional figure that stretches on forever in both directions.

line segment - A line with two points as ends.

### m

magnitude - The length of a vector.

### p

parabola - The set of all points (x,y) in a plane that is equidistant from a fixed line, the **directrix**, and a fixed point, the **focus**, not on the line. The midpoint between the focus and the **directrix** is the vertex and the line passing through the focus and the vertex is the **axis** of the parabola.

plane - A flat, two dimensional surface that is infinitely large.

### s

slope - Measure of a straight line's steepness or slant.

### v

variable - A symbol, usually a letter, that represents an unknown value.

vector - A directed line segment with an initial point and a terminal point.