# On graphing polar functions

• Jan 28th 2010, 10:56 PM
Jukodan
On graphing polar functions
I've been teaching myself Calculus II and polar coordinates are giving me the hardest time. I know there are two methods for graphing a polar functions, you can compile a table of values or you can refer to the Cartesian graph of the function itself. For $r =1-2 \cos(\theta)$ I have been trying the latter method to no avail. The problem is I don't know in what increments to label the x-axis for the graph. People usually say set $\theta = \frac{\pi}{2}$ and solve for $\theta$ and that's how you get your increments, but in this case I get funky answers. Someone please.
• Jan 28th 2010, 11:06 PM
Calculus26
when graphing something llike

r = 1- 2cos(t) ( a limacon)

in addition to multiples of pi/2 also locate the zeroes as these are where

r can change from pos to neg

1-2cos(t) = 0 t = pi/3, 5pi/3 so include these values as well as the usual suspects pi/2,pi,3pi/2, and 2pi

when graphing r = a cos(nt) or asin(nt) consider multiples of pi/(2n)

This will give you the values where r= -a,0 and a

For a more complete discussion see Polar Coordinate System
• Jan 29th 2010, 09:54 AM
Jukodan
This is why I love you guys.