From http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indeng.html#c1, for calculating the energy stored in an inductor:(adsbygoogle = window.adsbygoogle || []).push({});

[tex]P=Li\frac{di}{dt}[/tex]

[tex]E=\int_{0}^{t}Pdt=\int_0^ILidi=\frac{1}{2}LI^2[/tex]

Is there a theorem that says it's okay to just cancel out the dt in that second equation, and then replace the limits of integration?

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# How is this derivation valid?

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