Changes

A '''torus''' is the mathematical term for a tire-like shape created by rotating a [[circle]] around the [[x-axis]].   

A '''torus''' is the mathematical term for a tire-like shape created by rotating a [[circle]] around the [[x-axis]].   

If the “inner [[radius]]” (the width of the doughnut hole) is R, and the radius of the circular cross-section is r, then, the [[surface area]] of the torus is

If the “inner [[radius]]” (the width of the doughnut hole) is <math>R</math>, and the radius of the circular cross-section is <math>r</math>, then, the [[surface area]] of the torus is

:S = 4 &pi;² (R+r)r

:<math>S = 4 \pi^2 (R+r)r</math>

and the [[volume]] is

and the [[volume]] is

:V = 2 &pi;²(R+r)r²

:<math>V = 2 \pi^2 (R+r)r^2</math>