# Thread: Graphing w/TI-85 and polar coordinates

1. ## Graphing w/TI-85 and polar coordinates

Does anyone know how to graph this:

Inside r=a(1+cos pheta) and outside r=a cos pheta

Thanks!

2. Originally Posted by Possible actuary
Does anyone know how to graph this:

Inside r=a(1+cos pheta) and outside r=a cos pheta

Thanks!
I used Maple to graph the curves (letting a=2)

a:=2:
plot([a*(1+cos(theta)),a*cos(theta)],theta=0..2*Pi,
coords=polar,thickness=3,color=[red,blue]);

3. Originally Posted by Possible actuary
Does anyone know how to graph this:

Inside r=a(1+cos pheta) and outside r=a cos pheta

Thanks!
Hello,

1. you have to switch your calculator to polar mode.

2. Enter the equations at r1 and r2 in the y-editor. You'll find the $\displaystyle \theta$ at the $\displaystyle \boxed{X,T,\theta,n}$-key of your calculator.

3. Use the following window-settings:
$\displaystyle \theta$min = 0
$\displaystyle \theta$max = 6.2831... the means it is 2$\displaystyle \pi$
$\displaystyle \theta$step = .1308996... that means it is $\displaystyle \frac{\pi}{24}$
xmin = -2
xmax = 5
xscl = 1
ymin = -3
ymax = 3
yscl = 1

4. I've attached the drawing.

5. I used a TI84 and I hope that the syntax is the same with a TI85. If not

Remark: Unfortunately the factor 2 is hidden by the cursor in the equation r1