GEOMETRY - INTRODUCTION

• Point

  most basic term of all geometric concepts.

  it has only a location

  it has no size

  it can be modeled by a dot

  a point is named using a capital letter.
• Line

  a set of points

  it is straight

  Has an infinite length

  It has no thickness

  it is named by a single lowercase script letter or any two points on the line.
• Plane

  has length and width

  has no thickness

  it is a flat surface

  it extends infinitely

  it is named by a single script capital letter or by three points in the plane.
• Postulate 1:1

  Through any two points, there is exactly one line
• Postulate 1:2

  if two distinct lines intersect, then they intersect at exactly one point.
• Postulate 1:3

  If two distinct planes intersect, they intersect in exactly one line.
• Postulate 1:4

  through any three non collinear points there is exactly one plane.
• Flat-plane postulate

  if two points are in a plane, then the line containing the points is in the same plane.
• Line segment

  has two endpoints and all points on the line between those two points.
• Ray

  has one endpoint and all the points in one direction on its line.
• Angle

  is formed by two rays meeting at a common endpoint
• complementary angles

  two angles whose sum is 90
• supplementary angles

  Sum is 180
• Adjacent angles

  two angles who share a common endpoint and common side, but share no interior points.
• Vertical angle

  two angles formed by intersecting lines and facing in the opposite direction.

  they are congruent
• congruent angles

  same measure
• linear pair

  two angles that form a line