# Review Packet 3: Geometry

### 27 terms by math1s

#### Study  only

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Key vocabulary over statistics and probability.

### measure of an interior angle of a regular polygon

"the sum of all angles divided by the number of angles"

### regular polygon

a polygon with equivalent sides and angles

(n - 2)180

always 360

### measure of an exterior angle of a regular polygon

"the sum of all angles divided by the number of angles"

360/n

### point of concurrency

where three lines meet/intersect

### "regular" polygon

equal sides and equal angles

### Centroid of a triangle

point of concurrency of the medians; always inside the triangle

### median

cuts a line segment in half

### Incenter of a triangle

point of concurrency of the angle bisectors; always inside the triangle

### angle bisector

cuts an angle in half

### Circumcenter of a triangle

point of concurrency of perpendicular bisector; can be inside or outside of the triangle

### perpendicular bisector

A line that is perpendicular to a segment at its midpoint.

### Orthocenter of a triangle

point of concurrency of the altitudes; can be inside or outside of the triangle

### altitude

goes from the vertex to the opposite side, forming a 90 degree angle

### vertical angles

a pair of opposite congruent angles formed by intersecting lines

### complementary angles

Two angles whose sum is 90 degrees

### supplementary angles

Two angles whose sum is 180 degrees

### distance formula

d = √[( x₂ - x₁) + (y₂ - y₁)]

### midpoint formula

M = [ (x₁ + x₂) / 2, (y₁ + y₂) / 2 ]

### perpendicular lines

lines that form a 90 angle; their slopes are opposite reciprocals.
Ex: if the slope of a line is 1/2, the slope of the perpendicular line is -2.

### parallel lines

lines that have the same slope, so they never intersect

### perimeter

the some of all sides

### area

the number of square units needed to cover a flat surface

Example: