<math display='block'> <mmlrow> <mmlsub> <mmli>m</mi> <mmli>e</mi> </msub> <mmlo>=</mo><mmlsub> <mmlsup> <mmli>A</mi> <mmlo>&#x2032;</mo> </msup> <mmli>o</mi> </msub> <mmli>&#x0394;</mi><mmlo stretchy='false'>(</mo><mmlsub> <mmli>&#x03C1;</mi> <mmli>o</mi> </msub> <mmlo>&#x2212;</mo><mmli>&#x03C1;</mi><mmlo stretchy='false'>)</mo> </mrow> </math>