n class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.43056em;vertical-align:0em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">&#x3C0;</span></span></span></span> * <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><msup><mi>r</mi><mn>2</mn></msup></mrow><annotation encoding="application/x-tex">r^2</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><