Geometry Chapter 1 Essentials of Geometry 1.1 Identify Points, Lines, and Planes

Undefined Terms have no formal definitions, but there is agreement about what they mean point line plane

Point (A) : we just think about it being a dot in space or in a plane that represents a specific location. A A point is represented by a capital letter

Line: A line is represented by two points and a line with think about it being an infinite number of points connecting in a straight orientation moving in both directions forever A line is represented by two points and a line with two arrow heads on each end l A B line l

Plane You name a plane using 3 noncollinear points. Plane ABC Think of a plane as being a 2 dimensional flat surface that continues forever without bending. 3 noncollinear points if connected create a triangle that lies in a plane. You name a plane using 3 noncollinear points. Plane ABC

Defined Terms Line segment ray

part of a line with two endpoints Line Segment: part of a line with two endpoints A line is represented by two points and a line with two points on each end A B

part of a line that has one endpoint Ray part of a line that has one endpoint A ray is represented by one points and a line with one arrow head A B

Opposite Rays An opposite ray is represented by a shared endpoint points and a line with one arrow head pointing in the opposite direction C B A

Collinear: When points lie on the same line they are collinear. The word betweeness in geometry implies that all points are collinear A lies between C and B. A, B, C are collinear. A B C

When points lie on the same plane they are coplanar. F H D B C G

Parallel Planes Parallel planes are planes that DO NOT intersect.

Perpendicular Planes Perpendicular planes intersect at a right angle. b a c

Intersecting Planes Planes that intersect create a line at all of the intersecting points.