# Points, Lines, and Planes

## In order to start our journey into Geometry, we first have to understand the meaning of some key terms!

## Part 1

**coplanar**(lie on plane

*A*). Planes are determined by three points (points are determined by one, and lines by two!). Plane

*A*has dotted "edges" because it extends infinitely in all directions! Think of a plane as a floor that extends infinitely. 2. Move point H so it lies outside of plane A. 3. Move the line so it contains point H and intersects the plane at point F. Points H and F are

**collinear**because they lie on the same line (). 3. Move the line segment to create line segment . 4. Move the ray to create ray .

## Part 2: Intersections between two lines

Take a few minutes to mess around with the toolbar below. Create a point, draw a line, make a triangle, draw a picture! Have a leetle fun! Then answer the following question: There are three cases of relations ("intersections") between two lines. What are they? Show one case using the toolbox below! Remember that a line is determined by two points, so start by adding two points before drawing a line between them.

## Part 3: Intersections of a plane with a line

1. In the image below, where does line intersect plane *P*?

2. In the image below, where does line intersect plane *P*?

3. Where does line intersect plane *P*?

## Part 4: Intersecting Planes

1. Where does plane *A *intersect with plane *B*?

2. There are two other cases of relations ("intersections") between two planes. What are they? [Hint: Think about two pieces of paper with "edges" that extend infinitely in all four directions of the paper.]