Geometry Chapter 1 Theorems, Postulates, Definitions

Front 1

Definition: Collinear

Back 1

Two or more points that lie on the same line.

Front 2

Definition: Non-Collinear

Back 2

Points that do not lie on the same line.

Front 3

Definition: Coplaner

Back 3

Two or more points that lie on the same plane.

Front 4

Segment Addition Postulate

Back 4

If Q is between P and R, then PQ + QR = PR. If PQ + QR = PR, then Q is between P and R.

Front 5

Pythagorean Theorem

Back 5

If a triangle is right, then the sum of the squares of the measures of the legs equals the square of the measure of the hypotenuse.

Front 6

Definition of a Midpoint

Back 6

The midpoint M of PQ is the point between P and Q such that PM = MQ.

Front 7

Midpoint Formula

Back 7

1. On a number line, the coordinate of the midpoint of a segment whose endpoints have coordinates a and b is (a+b)/2.
2. In a coordinate plane, the coordinates of the midpoints of a segment whose endpoints have coordinates (x1, y1) and (x2, y2) are ((x1 + x2)/2, (y1 + y2)/2).

Front 8

What is the interior of an angle?

Back 8

Front 9

What is the exterior of an angle?

Back 9

Front 10

Angle Additon Postulate

Back 10

If R is in the interior of <PQS, then m<PQR + m<RQS = m<PQS.
If m<PQR + m<RQS = m<PQS, then R is in the interior of <PQS.

Front 11

Definition of a right angle

Back 11

<A is a right angle if m<A is 90.

Front 12

Definition of an obtuse angle

Back 12

<A is an obtuse angle if m<A is greater than 90 and less than 180.

Front 13

Definition of an acute angle

Back 13

<A is an acute angle if m<A is less than 90.

Front 14

Perpendicular Lines are:

Back 14

special intersecting lines that form right angles.

Front 15

Vertical Angles:

Back 15

are congruent.