Proofing

_psets/5.md

@@ -172,7 +172,10 @@ mil is a thousandth of an inch), what is the inner diameter?
 Solving the formula above for $$r_i$$,
 
 $$
-r_i = r_0 \cdot e^{-2 \pi \cdot 51.6 \sqrt{\epsilon_0 \epsilon_r / \mu_0}}
+\begin{align*}
+r_i &= r_0 \cdot e^{-2 \pi \cdot 51.6 \sqrt{\epsilon_0 \epsilon_r / \mu_0}} \\
+&= 8.2 \si{mils}
+\end{align*}
 $$
 
 ### (e)
@@ -181,10 +184,12 @@ $$
 For RG58/U, at what frequency does the wavelength become comparable to
 the diameter?
 
-We know $$\lambda \nu = c$$, so
-
 $$
-\num{2e8} \si{m/s} \cdot \frac{1}{2 \cdot \num{1.48e-3} \si{m}} = \num{6.76e10} \si{Hz}
+\begin{align*}
+\nu &= \frac{c}{\lambda} \\
+&= \frac{\num{2e8} \si{m/s}}{2 \cdot \num{1.48e-3} \si{m}}  \\
+&= \num{6.76e10} \si{Hz}
+\end{align*}
 $$