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# What is the function for the number 8? [Solved!]

### My question

what is the function of the #8

### Relevant page

4. The Graph of a Function

### What I've done so far

Some trial and error, and examples on your page.

X

what is the function of the #8
Relevant page

<a href="/functions-and-graphs/4-graph-of-function.php">4. The Graph of a Function</a>

What I've done so far

Some trial and error, and examples on your page.

## Re: What is the function for the number 8?

hello Sherry

I'm not sure whether your question means "What is the function such that when you graph it, it will give you the shape that looks like the number 8." Is that what you're trying to do?

If so, you need to use Polar Coordinates, which you can find at 7. Polar Coordinates.

For your problem, if you graph r = sin theta from 0 to pi, you get a circle, diameter 1 with the bottom of the circle going through the origin (0,0).

Now, what you want is another circle below the original circle as you go from pi to 2 pi. As a hint, the radius for the bottom circle must be positive.

Is that enough to get you started?

Good luck with it

Regards

Murray Bourne

X

hello Sherry

I'm not sure whether your question means "What is the function such that when you graph it, it will give you the shape that looks like the number 8." Is that what you're trying to do?

If so, you need to use Polar Coordinates, which you can find at <a href="/plane-analytic-geometry/7-polar-coordinates.php">7. Polar Coordinates</a>.

For your problem, if you graph r = sin theta from 0 to pi, you get a circle, diameter 1 with the bottom of the circle going through the origin (0,0).

Now, what you want is another circle below the original circle as you go from pi to 2 pi. As a hint, the radius for the bottom circle must be positive.

Is that enough to get you started?

Good luck with it

Regards

Murray Bourne

## Re: What is the function for the number 8?

Thanks.

Does r=-sin theta work for the bottom part?

Is it possible to do it with one function?

X

Thanks.

Does r=-sin theta work for the bottom part?

Is it possible to do it with one function?

## Re: What is the function for the number 8?

Well, r=-sin theta does work, but you need to specify the range of values for theta as part of your definition.

Can you do it with one function?

X

Well, r=-sin theta does work, but you need to specify the range of values for theta as part of your definition.

Can you do it with one function?

## Re: What is the function for the number 8?

Is it this?

r = sin theta for 0 <= theta < pi

r = -sin theta for pi <= theta < 2pi

X

Is it this?

r = sin theta for 0 &lt;= theta &lt; pi

r = -sin theta for pi &lt;= theta &lt; 2pi

## Re: What is the function for the number 8?

Correct! It's not really a "single function", but it's probably the best we can do for this case.

We could also write it as

r^2 = sin theta for 0 <= theta < pi

X

Correct! It's not really a "single function", but it's probably the best we can do for this case.

We could also write it as

r^2 = sin theta for 0 &lt;= theta &lt; pi