10.7 Polar Coordinates Adapted by JMerrill, 2011
Polar Coordinate Systems Copyright © by Houghton Mifflin Company, Inc. All rights reserved. 2 You’ve all seen a polar coordinate system (the movies). Polar coordinates are used in navigation and look like
Copyright © by Houghton Mifflin Company, Inc. All rights reserved. 3 The polar coordinate system is formed by fixing a point, O, which is the pole (or origin). Definition: Polar Coordinate System = directed angle Polar axis r = directed distance O Pole (Origin) The polar axis is the ray constructed from O. Each point P in the plane can be assigned polar coordinates (r, ). P = (r, ) r is the directed distance from O to P. is the directed angle (counterclockwise) from the polar axis to OP.
Copyright © by Houghton Mifflin Company, Inc. All rights reserved. 4 Plotting Points The point lies two units from the pole on the terminal side of the angle units from the pole Plotting Points
Copyright © by Houghton Mifflin Company, Inc. All rights reserved. 5 Multiple Representations of Points There are many ways to represent the point We will only use 1 point instead of multiple representations.
Copyright © by Houghton Mifflin Company, Inc. All rights reserved. 6 Polar and Rectangular Coordinate (r, ) (x, y) Pole x y (Origin) y r x The relationship between rectangular and polar coordinates is as follows. The point (x, y) lies on a circle of radius r, therefore, r 2 = x 2 + y 2.
Coordinate Conversion To convert from polar to rectangular: x = r cosθ y = r sinθ To convert from rectangular to polar: tanθ = x 2 + y 2 = r 2 Copyright © by Houghton Mifflin Company, Inc. All rights reserved. 7
8 Example: Coordinate Conversion Coordinate Conversion – the Relationship (Pythagorean Identity)
Example Convert to rectangular coordinates Copyright © by Houghton Mifflin Company, Inc. All rights reserved. 9
10 Example: Coordinate Conversion Example: Convert the point (1,1) into polar coordinates.
Copyright © by Houghton Mifflin Company, Inc. All rights reserved. 11 Graphs of Polar Equations Example: Graph the polar equation r = 2cos –2 – r The graph is a circle of radius 2 whose center is at point (x, y) = (0, 1). Radian mode Polar mode
Copyright © by Houghton Mifflin Company, Inc. All rights reserved. 12 Special Polar Graphs: Limaçon Each polar graph below is called a Limaçon. –3 – –3
Copyright © by Houghton Mifflin Company, Inc. All rights reserved. 13 Special Polar Graphs: Lemniscate Each polar graph below is called a Lemniscate. –55 3 –3 –5 5 3 –3
Copyright © by Houghton Mifflin Company, Inc. All rights reserved. 14 Special Polar Graphs: Rose Curve Each polar graph below is called a Rose curve. The graph will have n petals if n is odd, and 2n petals if n is even. –5 5 3 –3 –5 5 3 –3 a a