where is the slantheightof the figure, is the perimeterof the base,and is the area of the base.
Imaginea seriesof pyramidsin which , the numberof sidesof eachfigure’s base,increases.
As you can see, as increases,the figuremoreand moreresemblesa circle.So in a sense,a circleap-
proachesa polygonwith an infinitenumberof sidesthat are infinitelysmall.
In the sameway, a coneis like a pyramidthat has an infinitenumberof sidesthat are infinitelysmallin
length.
Giventhis idea,it shouldcomeas no surprisethat the formulafor findingthe total surfacearea of a coneis
similarto the pyramidformula.The only differencebetweenthe two is that the pyramiduses , the
perimeterof the base,whilea coneuses , the circumferenceof the base.
SurfaceAreaof a RightConeThe surfacearea of a right coneis givenby:Sincethe circumferenceof a circleis :