math question

[Don Shepherd]

or maths, if you are not in the US

I am trying to graph circles on my TI-84 plus graphing calculator. I know that the formula for a circle is (x-h)^2 + (y-k)^2 = r^2 where the center of the circle is (h,k) and the radius is r, but to actually graph the circle I need two formulas (one for the upper part, one for the lower) in the form y1= and y2=, using variables x, h, k, and r.

I have found several formulas on the Internet, but none give me the results that I would expect.

[SlideRule]

How do I graph a circle on a TI graphing calculator?
Functions can be graphed on TI graphing calculators in the form Y in terms of X.
In order to graph a circle, the function for a circle would need to be solved for Y, ie to graph the unit circle (x2+y2=1), first, solve for y, and then input the results into the Y= Editor

source: "Graphing a Circle on a TI Graphing Calculator. - Knowledge Base by Texas Instruments - US and Canada"

BEST!
SlideRule

[Manolo Sobrino]

Why don't you try a parametric plot?

Mode->Par
\begin{equation}
X_{1T} = h + r*cos(T)
\end{equation}
\begin{equation}
Y_{1T} = k + r*sin(T)
\end{equation}
Zoom->ZSquare or ZDecimal or ZInteger

If you insist on using Cartesian coordinates, then

Mode->Func
\begin{equation}
Y_{1} = k +\sqrt{r^2-(x-h)^2}
\end{equation}
\begin{equation}
Y_{2} = k -\sqrt{r^2-(x-h)^2}
\end{equation}
Zoom->ZSquare or ZDecimal or ZInteger

[Don Shepherd]

Thanks SlideRule and Manolo, that's exactly what I was looking for.

[klesl]

You can use following application for this task
https://education.ti.com/en/us/software/...icgraphing

There are 4 shapes - circle, ellipse, hyperbola and parabola

[Don Shepherd]

Thanks Klesl, that is a good reference.