Fix typo in equation in section 3.12.3

Resolves #1686

Author: hollasch

CHANGELOG.md

@@ -14,6 +14,7 @@ Change Log / Ray Tracing in One Weekend
 ### The Next Week
 
 ### The Rest of Your Life
+  - Fix    -- Typo in equation in book 3, section 12.3 (#1686)
 
 
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books/RayTracingTheRestOfYourLife.html

@@ -3695,7 +3695,7 @@
 
   $$ r_2 = 2\pi \cdot C \cdot (1-\cos(\theta)) $$
   $$ 1 = 2\pi \cdot C \cdot (1-\cos(\theta_{max})) $$
-  $$ C = \frac{1}{2\pi \cdot (1-\cos(\theta_{max})} $$
+  $$ C = \frac{1}{2\pi \cdot (1-\cos(\theta_{max}))} $$
 
 Which gives us an equality between $\theta$, $\theta_{max}$, and $r_2$: