typo fix, closes #111

src/1_einstein_model.md

@@ -247,7 +247,7 @@ $$
 n_B(\omega,T) = \frac{1}{e^{\hbar\omega/k_B T} - 1}.
 $$
 
-Substituting $n_B$ into, the expression for the oscillator energy, obtain the expectation value of the energy stored in the oscillator at temperature $T$—the *thermal energy*:
+Substituting $n_B$ into, the expression for the oscillator energy, we obtain the expectation value of the energy stored in the oscillator at temperature $T$—the *thermal energy*:
 $$
 \begin{align}
 \langle E \rangle &= \frac{1}{2}\hbar\omega_0+\hbar\omega_0 \langle n \rangle \\