Topic: calculate area and perimeter of circle

I am having an issue calculating the area and perimeter of a circle.
I drew a circle through "relation". Is that the problem?
Even when drawing through "parametric function" I am having issues.
Any help would be greatly appreciated! (especially when drawing through "relation" as I find that more simple).

Re: calculate area and perimeter of circle

Unfortunately Graph cannot do calculations on relations, so you have to use a parametric function instead.

If your circle is centered at (0,0), you can use a polar function. For example r(t)=5 will plot a circle with radius 5. If you want to calculate the area of the whole circle you can use $matches[1] with From=0 and To=2pi. Likewise if you want to calculate the whole perimeter you can use $matches[1] with From=0 and to=2pi.