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

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

The equation is x^2 + y^2 = 9

2. ## 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:

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

Polar method

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

Parametric method

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

You can change the type of graphing method in the setup menu of your TI.

3. ## Re: How do you graph a circle with the TI-83 plus calculator?

What is the preferred method?

4. ## 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).

5. ## Re: How do you graph a circle with the TI-83 plus calculator?

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.

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# how to graph a circle on a ti-83 plus

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