# Homework Help: Polar functions

1. Dec 9, 2005

### jacy

Hi
I am trying to find the area inside the lemniscate

r^2 = 2a^2 cos(2theta) a>0

I am having trouble graphing this in the calculator. I am in the polar mode. The a^2 is giving me problem. I am using TI 83 plus. Also i need the interval, for the above function. Please help, thank you. Once i have the interval i can find the area using

Surface Area = Integral (lower interval, upper interval) r^2 d(theta)

2. Dec 9, 2005

### hypermorphism

Unless the problem specifically asks you to use a calculator to graph the region, you shouldn't need one for this.
Graph some sample points using what you know about the cosine function and how cosine behaves in polar coordinates. If you still want the calculator, use it to graph the equation for a=1. 'a' is just a scalar you can easily incoporate into your interval if necessary.

3. Dec 16, 2005

### jacy

Thanks for the reply. But how can i find the interval.

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