**
Acute Angle
** -
An angle with a measure of less than 90 degrees.

**
Addition Properties of Inequality
** -
If *a* < *b*, then *a* + *c* < *b* + *c*

If *a* > *b*, then *a* + *c* > *b* + *c*

**
Greater Than
** - *a* > *b* if and only if there is a positive number *c* such that *a* - *c* = *b*.

**
Inequality
** -
A statement that shows the relationship between two (or more)
expressions with one of the following five signs: <, ≤, >,
≥, ≠.

**
Inequality Properties of Opposites
** -
If *a* > 0, then - *a* < 0

If *a* < 0, then - *a* > 0

**
Less Than
** - *a* < *b* if and only if there is a positive number *c* such that *a* + *c* = *b*.

**
Multiplication and Division Properties of Inequality
** -

**For positive numbers:**
If

*a* < *b* and

*c* > 0, then

*ac* < *bc* and

<
If

*a* > *b* and

*c* > 0, then

*ac* > *bc* and

>
**For negative numbers:**
If

*a* < *b* and

*c* < 0, then

*ac* > *bc* and

>
If

*a* > *b* and

*c* < 0, then

*ac* < *bc* and

<
**
Obtuse Angle
** -
An angle with a measure greater than 90 degrees, but not more than 180 degrees.

**
Property of Squares of Real Numbers
** - *a*^{2}≥ 0 for all real numbers *a*.

**
Right Angle
** -
An angle with a measure of exactly 90 degrees.

**
Subtraction Properties of Inequality
** -
If *a* < *b*, then *a* - *c* < *b* - *c*

If *a* > *b*, then *a* - *c* > *b* - *c*

**
Transitive Properties of Inequality
** -
If *a* < *b* and *b* < *c*, then *a* < *c*.

If *a* > *b* and *b* > *c*, then *a* > *c*.

**
Trichotomy Property
** -
For any two real numbers *a* and *b*, exactly one of the following is
true: *a* < *b*, *a* = *b*, *a* > *b*.