ss_8_2

ss_8_2 - Section 8.2 Equations and Graphs In this section,...

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Section 8.2 Equations and Graphs In this section, we cover the standard polar graphs. Most of these graphs have simple polar equations, but the graphs would be difficult to define in cartesian coordinates. Note: As with cartesian equations, when one plots a polar equation, e.g. r =s in θ , one plots the set of all points ( r, θ ) that satisfy the equation. Example. The graph of r = 2 is a circle of radius 2 centered at the origin, because we plot the set of all points ( r, θ ) such that r = 2. Note that most circles not centered at the origin have fairly complicated polar equations. Example. The graph of θ = π 3 is a line through the origin with slope 3. This is the graph of all ( r, θ ) such that θ = π 3 Example. The graph of r cos θ = 1 is the vertical line x = 1, because r cos θ = x and the polar equation r cos θ = 1 is equivalent to the cartesian equation x =1. Example. Graph r =2sin θ . Solution. We find the cartesian equation for r =2s θ . r 2 =2 r sin θ (multiply by r ) x 2 + y 2 y ( r 2 = x 2 + y 2 , y = r sin θ ) x 2 + y 2 - 2 y =0 x 2 +( y - 1) 2 =1 This last equation is the equation of a circle of radius 1 tangent to the x - axis as shown below.
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This note was uploaded on 12/11/2011 for the course MAC 1140 taught by Professor Kutter during the Fall '11 term at FSU.

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ss_8_2 - Section 8.2 Equations and Graphs In this section,...

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