Polar Equation: Draw and Fill in chart

**Binary** · Apr 12th 2012, 10:40 PM

Draw and fill in the chart that has a row for "Theta" and a row for "r" for this polar equation: r=1-3cos(theta)

I have to fill in the 24 spots (12 for theta and 12 for r) on the chart using this polar equation: r=1-3cos(theta).

The picture given is a unit circle counting by pi/12. Please help???

**a tutor** · Apr 12th 2012, 11:46 PM

Hve you been introduced to ...polar plot r=1-3cos(t) - Wolfram|Alpha ?

**Binary** · Apr 13th 2012, 08:06 AM

Thank you very much. How would I go about solving for R when cos(theta)= pi/12?

**skeeter** · Apr 13th 2012, 02:04 PM

Originally Posted by Binary

Thank you very much. How would I go about solving for R when cos(theta)= pi/12?

I think you mean ... "how can I evaluate $r$ when $\theta = \frac{\pi}{12}$ " ?

$r = 1 - 3\cos\left(\frac{\pi}{12}\right)$

... get out your calculator

$r \approx 0.966$

by hand ...

$\cos\left(\frac{\pi}{12}\right) = \cos\left(\frac{\pi}{3} - \frac{\pi}{4}\right)$

... use the difference identity for cosine.

**Binary** · Apr 13th 2012, 03:59 PM

Originally Posted by skeeter

I think you mean ... "how can I evaluate $r$ when $\theta = \frac{\pi}{12}$ " ?

$r = 1 - 3\cos\left(\frac{\pi}{12}\right)$

... get out your calculator

$r \approx 0.966$

by hand ...

$\cos\left(\frac{\pi}{12}\right) = \cos\left(\frac{\pi}{3} - \frac{\pi}{4}\right)$

... use the difference identity for cosine.

Yeah I figured it out finally then just saw your post. Thank you very much. I was trying to do it by hand btw.

**Binary** · Apr 13th 2012, 04:18 PM

When I use my calculator I dont get r=0.966. I get approx r=-1.897

**skeeter** · Apr 13th 2012, 04:36 PM

Originally Posted by Binary

When I use my calculator I dont get r=0.966. I get approx r=-1.897

you're correct ... I only punched in $\cos\left(\frac{\pi}{12}\right)$ , my mistake.

Thread: Polar Equation: Draw and Fill in chart

LinkBack

Thread Tools

Display

Polar Equation: Draw and Fill in chart

Re: Polar Equation: Draw and Fill in chart

Re: Polar Equation: Draw and Fill in chart

Re: Polar Equation: Draw and Fill in chart

Re: Polar Equation: Draw and Fill in chart

Re: Polar Equation: Draw and Fill in chart

Re: Polar Equation: Draw and Fill in chart

Similar Math Help Forum Discussions

Deriving cosine equation from a chart

[SOLVED] How to draw Polar Graphs

Need an example fill out please :)

NEED help for these fill-in problems!!

Fill in the Blanks.

Search Tags