<math display='block'> <mmlrow> <mmlstyle displaystyle='true'> <mmlrow> <mmlsubsup> <mmlo>&#x222B;</mo> <mmli>o</mi> <mmlrow> <mmlsub> <mmli>y</mi> <mmli>m</mi> </msub> </mrow> </msubsup> <mmlrow> <mmlo stretchy='false'>(</mo><mmli>d</mi><mmli>V</mi><mmlo>/</mo><mmli>d</mi><mmli>t</mi> </mrow> </mrow> </mstyle><mmlo stretchy='false'>)</mo><mmli>d</mi><mmli>y</mi><mmlo>=</mo><mmlstyle displaystyle='true'> <mmlunderover> <mmlo>&#x2211;</mo> <mmlrow> <mmli>j</mi><mmlo>=</mo><mmln>1</mn> </mrow> <mmli>N</mi> </munderover> <mmlrow> <mmlo stretchy='false'>[</mo><mmlsub> <mmlrow> <mmlo stretchy='false'>(</mo><mmlsub> <mmli>V</mi> <mmli>j</mi> </msub> <mmlo stretchy='false'>)</mo> </mrow> <mmli>t</mi> </msub> <mmlo>&#x2212;</mo><mmlsub> <mmlrow> <mmlo stretchy='false'>(</mo><mmlsub> <mmli>V</mi> <mmli>j</mi> </msub> <mmlo stretchy='false'>)</mo> </mrow> <mmlrow> <mmli>t</mi><mmlo>&#x2212;</mo><mmli>&#x03B4;</mi><mmli>t</mi> </mrow> </msub> <mmlo stretchy='false'>]</mo><mmli>&#x03B4;</mi><mmli>l</mi> </mrow> </mstyle><mmli>sin</mi><mmli>&#x03B8;</mi><mmlo>/</mo><mmli>&#x03B4;</mi><mmli>t</mi> </mrow> </math>