diff --git a/uni/mmme/2051_electromechanical_devices/ac_intro.md b/uni/mmme/2051_electromechanical_devices/ac_intro.md
index d680ee1..59f7514 100755
--- a/uni/mmme/2051_electromechanical_devices/ac_intro.md
+++ b/uni/mmme/2051_electromechanical_devices/ac_intro.md
@@ -75,9 +75,11 @@ Ohm's law generalised to incorporate complex resistance, reactance, $X$:
 
 \begin{align*}
 v &= iX \\
-V\angle\Phi_v &= i\angle\Phi_iX \\
-&= i\angle\Phi_ij\omega L \\
-\frac{V}{j\omega L}\angle\Phi_v &= I\angle\Phi_i
+V\angle\Phi_v &= I\angle\Phi_iX \\
+&= I\angle\Phi_ij\omega L \\
+\frac{V}{j\omega L}\angle\Phi_v &= I\angle\Phi_i\\
+\frac{{V}\omega L}\angle\left(\Phi_v - \frac{\pi}{2}\right) &= I\angle\Phi_i
+\end{align*}
 
 # Power