data/mathematical/67.mml
<math xmlns='http://www.w3.org/1998/Math/MathML' display='inline'><semantics><mrow><mfrac><mrow><mo>∂</mo><mi>f</mi></mrow><mrow><mo>∂</mo><mi>x</mi></mrow></mfrac><mo>=</mo><msub><mi>f</mi> <mi>x</mi></msub><mo>=</mo><msub><mo>∂</mo> <mi>x</mi></msub><mi>f</mi></mrow><annotation encoding='application/x-tex'>\frac{ \partial f}{ \partial x} = f_x = \partial_x f</annotation></semantics></math>