Basic Geometric Ideas

8-1 Vocabulary Words:

1. Point2. Line3. Plane4. Line segment5. Ray6. Parallel lines7. Intersecting lines8. Perpendicular

lines

When in life do you see points, lines, and line segments?

Problem Work with a partner. Each partner

should draw a house using points and line segments. Do not let your partner see your drawing.

Now have your partner try to draw your house by giving a verbal step-by-step description of what it looks like. Then repeat with the other partner and house. Compare drawings and discuss.

A point is an exact location in space. Name the points on the house.

A, B, C, D, E

• How else could you name line segment RS?

• Does it matter which letter comes first for a line segment?

• Could you name ray JK as ray KJ?

Line segment SR

No

No, because the endpoint is a J, and the name of a ray always starts with the name of its endpoint

• Why are perpendicular lines also called intersecting lines?

• What are lines called when they will not intersect?

• Can parallel lines be perpendicular?

By definition, perpendicular lines are intersecting lines that form square corners.

Parallel lines

No, because parallel lines never intersect

A line segment is part of a line having 2 endpoints. Name a line segment on the house.

If line segments AD and BC were extended in both directions forever, they would form lines. Since the lines stay the same distance apart and will never touch, they are called parallel lines.

If DC and BC were extended in both directions forever, they would form lines. These lines are perpendicular because they intersect to form a square corner.

Can you find other perpendicular lines and square corners?

AB, BA, BC, CB, CD, DC, DA, AD, DE, ED, AE, EA

Work with a partner

Name the following: 6 points 3 lines 2 line segments 1 set of parallel

lines 1 set of

perpendicular lines

Independent Practice