# How do you graph a circle with the TI-83 plus calculator?

• August 7th 2011, 08:19 PM
benny92000
How do you graph a circle with the TI-83 plus calculator?
The equation is x^2 + y^2 = 9
• August 7th 2011, 08:56 PM
Bacterius
Re: How do you graph a circle with the TI-83 plus calculator?
There are different ways to do it.

Cartesian method (y = f(x))

You will need two functions because of the limitations of the cartesian coordinate system, obtained by rearranging the circle equation in terms of x:

$y = \sqrt{9 - x^2}$ and $y = - \sqrt{9 - x^2}$

Polar method

This one is simple.. $r = 3$, since the radius of a circle is constant.

Parametric method

Use the trigonometric functions $X_t = 3 \cos{(t)}$ and $Y_t = 3 \sin{(t)}$.

You can change the type of graphing method in the setup menu of your TI.
• August 7th 2011, 11:15 PM
benny92000
Re: How do you graph a circle with the TI-83 plus calculator?
What is the preferred method?
• August 7th 2011, 11:23 PM
Bacterius
Re: How do you graph a circle with the TI-83 plus calculator?
Umm.. whichever, they all produce the same circle. It's up to personal preference and context.

I would personally recommend the parametric method because it's easy to change the center of the circle if you need to (as well as the radius of course).
• August 7th 2011, 11:24 PM
mr fantastic
Re: How do you graph a circle with the TI-83 plus calculator?
Quote:

Originally Posted by benny92000
What is the preferred method?

The prefered method depends on:

1. The circumstances.

2. What you prefer.

Personally, I don't see why a student would need a calculator to draw the graph of a circle.