# Intro to Euclidean Geometry

## Coordinate Plane Review

For more detailed review of coordinate planes and ordered pairs with examples, refer to the 6th Grade Math: Euclidean/Coordinate Plane, Ordered Pairs page

*What is a coordinate plane?*

A coordinate plane is a system that uses one or numbers (coordinates) to determine a position of a point.

The left-right (horizontal) direction is known as x (referred to as the **x-axis**).

The up-down (vertical) direction is known as y (referred to as the **y-axis**).

**However, that coordinate grid is just two-dimensional. It is possible for there to be a 3rd dimension in geometry -- this is where the z-axis comes in.**

**(x,y,z) = 3 coordinates to define a point**

Try visualizing it!

Watch the video

Use pencils and paper to imitate the behavior of the 3 planes

## Terms and Labels

**Point** – an exact location in space. A point has no dimension

**Line** **Segment** – a part of a line having two endpoints.

**Line** – a collection of points along a straight path that extends endlessly in both directions

**Ray** – a part of a line having only one endpoint

**Angle** – consists of two rays that have a common. The endpoint called the vertex of the angle.

**Plane** – a flat surface that extends endlessly in all directions.

**Collinear -** lying in the same straight line

**Coplanar** - lying on the same plane

Watch the video for a good review of what we just learned!

## Supplementary vs Complementary Angles

Angles are **supplementary** if the sum of their angles is 180 degrees (make up a straight angle!)

Angles are **complementary** if the sum of their angles is 90 degrees (make up a right angle!)

Practice:

If two angles are **complementary** and one of them is 52 degrees, what is the other one? Answer: 32 degrees (90-52=32, so 32+52=90)

If two angles are **supplementary** and one of them is 52 degrees, what is the other one? Answer: 128 degrees (90-52=128, so 128+52=180)

## Quiz!

## Check your answers!

Quiz answers (out of 10 points):

B

B

B

D

C

A

A

A, C

A