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Precalculus

The bridge between algebra and calculus: functions studied for their own sake — polynomial, rational, exponential, logarithmic — plus the complex numbers, sequences and series, conic sections and vectors that calculus will assume you know.

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Chapters from OpenStax Precalculus 2e

Every section of the book, condensed into a lesson with its own practice problems.

1. Functions

2. Linear Functions

3. Polynomial and Rational Functions

4. Exponential and Logarithmic Functions

6. Periodic Functions

10. Analytic Geometry

11. Sequences, Probability and Counting Theory

Symbols used here

|x|
absolute value / modulus
Distance from zero: |−3| = 3. For a complex number, distance from the origin.
\binom{n}{k}
binomial coefficient, "n choose k"
Number of k-element subsets of n things: n!/(k!(n−k)!).
\pi
pi
Ratio of a circle's circumference to its diameter, 3.14159…
e
Euler's number
2.71828…, the base whose exponential is its own derivative.
i
imaginary unit
i² = −1.
\theta
theta
The usual name for an angle.
\log_b x,\ \ln x
logarithm, natural log
The exponent b must be raised to for x; ln uses base e.
\mathbf{v},\ \vec{v}
vector
A quantity with magnitude and direction; a column of numbers.

Questions people ask

What is a function, really?

A rule that assigns exactly one output to each input. The vertical-line test on a graph is the same idea: no input may have two outputs.

Why do we need complex numbers?

Because x² + 1 = 0 has no real solution, and allowing one new number i with i² = −1 makes every polynomial equation solvable. They then turn out to describe rotation, waves and alternating current more naturally than real numbers do.

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