1.1 Identify Points, Lines and Planes

•Undefined Terms (terms that do not have formal definitions but have an understood

meaning)PointLinePlane

1.1 Identify Points, Lines and Planes

Point: has no dimension. It is represented by a dot.

Line: has one dimension. It is represented by a line with two

arrowheads, but it extends without end.Plane: has two dimensions. It is

represented by a shape that looks like a floor or a wall, but it extends w/o end.

1.1 Identify Points, Lines and Planes

Collinear points are:

Points that lie on the same line.

Coplanar points are:

Points that lie on the same plane.

Example 1:

a. Give two other names for Line PQ and for plane R.

b. Name three points that are collinear and Name four points that are coplanar.

1.1 Identify Points, Lines and Planes

1.1 Identify Points, Lines and Planes

Defined terms: terms that can be described using known words.

Segment: the line segment AB, or segment AB, consists of the endpoints A and B and

all the points that lie on line AB that are between A and B.

Ray: The ray AB consists of the endpoint A and all the points on line AB that lie on the

same side of A as B.

If C lies on line AB between A and B, then ray CA and ray CB are opposite rays.

Segments and rays are collinear if they lie on the same line. So, opposite rays are collinear. Lines, segments and rays are coplanar if they lie on the same plane.

1.1 Identify Points, Lines and Planes

EXAMPLE 2:

a. Give another name for Segment PM.

b. Name all rays with endpoint Q. Which of these rays are opposite rays?

1.1 Identify Points, Lines and Planes

Two or more geometric figures intersect if they have one or more points in common. The intersection of the figures is the set of

points the figures have in common.

The intersection of The intersection of

two lines is a point. two planes is a line.

1.1 Identify Points, Lines and Planes

Example 3:

a. Sketch a plane and two intersecting lines that intersect the plane at separate points.

b. Sketch a plane and two intersecting lines that do not intersect the plane.

c. Sketch a plane and two intersecting lines that lie in the plane.

1.1 Identify Points, Lines and Planes

Example 3:d. Sketch a plane and a line that is in the

plane.

e. Sketch two planes that do not intersect in a line.

f. Sketch three lines that lie in a plane and intersect at one point.

1.1 Identify Points, Lines and Planes

• Can two planes intersect in a segment? Explain.

• Can a line intersect a plane in only two points? Explain.

1.1 Identify Points, Lines and Planes