Merge pull request #520 from vicha-w/main

Fixed typeset in (optional) policy gradient theorem

units/en/unit4/pg-theorem.mdx

@@ -28,9 +28,9 @@ We then multiply every term in the sum by \\(\frac{P(\tau;\theta)}{P(\tau;\theta
 \\( = \sum_{\tau} \frac{P(\tau;\theta)}{P(\tau;\theta)}\nabla_\theta P(\tau;\theta)R(\tau) \\)
 
 
-We can simplify further this since \\( \frac{P(\tau;\theta)}{P(\tau;\theta)}\nabla_\theta P(\tau;\theta)\\). 
+We can simplify further this since \\( \frac{P(\tau;\theta)}{P(\tau;\theta)}\nabla_\theta P(\tau;\theta) =  P(\tau;\theta)\frac{\nabla_\theta P(\tau;\theta)}{P(\tau;\theta)}  \\). 
 
-Thus we can rewrite the sum as \\( =  P(\tau;\theta)\frac{\nabla_\theta P(\tau;\theta)}{P(\tau;\theta)}  \\)
+Thus we can rewrite the sum as
 
 \\( P(\tau;\theta)\frac{\nabla_\theta P(\tau;\theta)}{P(\tau;\theta)}= \sum_{\tau} P(\tau;\theta) \frac{\nabla_\theta P(\tau;\theta)}{P(\tau;\theta)}R(\tau) \\)