# MandysNotes

## Mandy

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### Sets of Numbers Examples Sets: Natural Numbers, Whole numbers, Integers

20 March 2010

Counting Numbers:

### {1, 2, 3, 4, 5, 6, ...}

BY THE WAY, "..." notates continuation going up infinitely.

The set of Natural Numbers $$\mathbb{N}\ \$$ = {0, 1, 2 3, 4, 5, 6...}.

The set of Integers, $$\mathbb{Z}\ \$$   = {..., -3, -2, -1, 0, 1, 2, 3}.

The set of Rational numbers, $$\mathbb{Q}\ \$$  is the set of ratios of integers.

That is, every $$q \in \mathbb{Q}\$$

is of the form:

$$q = \frac{n}{m} \$$

With $$n, m \in \mathbb{Z}\$$ .

The set of Real Numbers $$\mathbb{R}\ \$$  is the set of limits of sequences of rational numbers.

### Sets of Numbers

20 March 2010

A set is a collection of "elements," or "members," and each set is entirely determined by its members. If $x$is a member of a set $U,$ we write $x \in U.$ In basic algebra, the elements of a set are usually numbers.

We can also designate a set by enclosing its members in  braces , {   }.

### Introduction to Algebra: Variables & Constants

20 March 2010

All equations have various parts.  The variable represents the unknown.  We can tell what "x" represents in this particular equation, almost by guessing.  WHAT + 23 = 45?

The VARIABLE here is "x"

The CONTANT is 23, because it is "constantly" there, and we have already identified its value as 23.

Mathematically, we can obtain what "WHAT" equals, by subtracting 23 from 45.

45 - 23 = 22

Therefore, x = 22

### Trig Values of Special Angles

05 February 2010

Disclaimer: I did not create nor do I own these videos. I have simply embedded them, courtesy of YouTube.

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