# 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!

Quiz answers (out of 10 points):

1. B

2. B

3. B

4. D

5. C

6. A

7. A

8. A, C

9. A