<p>Notes/Examples for Intro to Coordinate Geometry</p><p>History The use of geometry dates back to before the beginning of history. However, it was often used in a very practical manner. It wasn't till about 600 BC that mathematicians began using formal logic and reasoning.</p><p>Rene Descartes was the man who is responsible for the Cartesian plane (or the x-y graph). He created it in the early 1600s. Surprisingly, he was a philosopher (considered one of the fathers of philosophy) and used his reasoning and logic skills in mathematics and science. One of his famous quotes is "I think, therefore I am."</p><p>Later on in history, Albert Einstein built foundational work in geometry to help create and prove his theory of relativity.</p><p>Some definitions to keep in mind throughout this unit: Coordinate plane--a two-dimensional surface on which a coordinate system has been set up; invented by Rene Descartes; also called Cartesian plane, graph, coordinate grid Coordinates--the numbers in an ordered pair that locate a point in the coordinate plane Ordered pair--a pair of numbers, written as (x,y), that represents a point on a coordinate grid Line segment--the part of a line between two points on the line, including the two points X-axis--the horizontal number line on a coordinate grid Y-axis--the vertical number line on a coordinate grid Quadrants, Origin To plot points, always write the x value first and then the y value. Ex. (2, 3) (3, -1) (-2, 3) (-3, -2)</p><p>Each of these points represents a point in each of the four quadrants (go through I to IV). -give students coordinates and they have to give the correct quadrant</p><p>A few examples: Here are some given points: A(1,1) B(1,4) C(5,4) D(5,1) Join these points and find the area of the figure.</p><p>Here are some given points: A(-2,-3) B(-6,-3) C(-2,-7) Find the missing point to make a square. Calculate the area.</p><p>Draw this one on the overhead and let students work through it. Given points A(3,1) B(-1,3) C(-3,0) D(1,-1) find the area of the polygon ABCD Hint: area of polygon = area of rectangle - total area of shaded triangles</p>