**
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*
.