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Explore the history of geometry and learn about the fundamental concepts of points, lines, and planes. Discover the significance of collinear and coplanar points and delve into the basic postulates that form the foundation of geometry.
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•Geometry is by far the oldest branch of mathematics.• Every ancient civilization developed some form of geometry, as a way of helping withsurvival.
•Geometry as we know it today was first developed by Greeks who lived in what is now Egypt.
•Geometry was formally organized by the mathematician Euclid in a book called The Elementsaround 300 B.C.
•Every geometry book for the past 2,300 years has been based on Euclid’s Elements.
Geometry• literally means “earth measure”• study of shapes and their relationships
•point • a location, usually represented by a dot • points are infinitely small • no length, width, or thickness • 0 dimensions
• We typically represent points with dots and name them with capital letters.
• line • shortest path from one point to another • infinitely thin; no thickness• extends forever in opposite directions • 1 dimension
•Lines are named with TWO points (not 3 or more)•You put a line symbol (double arrow) above the name of a line.
•Lines can also be named with small cursive (or italic) letters. These are lines l and m .
• plane •flat surface with no thickness and no boundaries•extends forever, but infinitely thin•2 dimensions
•We most often show planes by drawing a parallelogram (or other four-sided shapes)
•You can also name a plane with three points that are on it, like ABC.
In most cases we will just consider single planes, but we can also talk about•space •all the possible points in 3 dimensions
• Segment •Connects two points •Stops at the endpoints•Named by putting a bar above the endpoints
• Ray •Extends endlessly in one direction •Starts at an endpoint and continues.
• Named with an endpoint and one other point on the ray, with an arrow above them.(The first letter must be the endpoint.)
• Opposite rays •Share the same endpoint •Together make a line
Postulate A statement that is so obvious we assume it is true without questioning it.
Euclid built all of geometry from just 5 postulates.We’ll use a lot more, 4 of which we’ll learn today.
Know … History of geometry Point, line, plane, space Collinear, coplanar Segment, ray, opposite rays Postulate 4 basic postulates of points, lines, & planes