data/mathematical/89.mml
<math xmlns='http://www.w3.org/1998/Math/MathML' display='inline'><semantics><mrow><msup><mi>σ</mi> <mn>2</mn></msup><mo>=</mo><msup><mi>X</mi> <mi>T</mi></msup><mi>V</mi><mi>X</mi></mrow><annotation encoding='application/x-tex'>\sigma^2 = X^TVX</annotation></semantics></math>