Fix division sign error in Quick Reference (#766)

Fixed the sign error in Math Reference -> Complex Arithmetic -> Division. 

Co-authored-by: Vincent van Wingerden <[email protected]>

Author: japanavi

quickref/qsharp-quick-reference.pdf

@@ -721,7 +721,7 @@
     $ (a + bi)  (c + di) $         & $ a \cdot c + a \cdot di + b \cdot ci + (b \cdot d)i^2 =$ \newline
                                      $ = (a \cdot c - b \cdot d) + (a \cdot d + b \cdot c)i $ \\
 	  Complex conjugate              & $ \overline{a + bi} = a - bi $ \\
-    Division $ \frac{a+bi}{c+di} $ & $ \frac{a+bi}{c+di} \cdot 1 = \frac{a+bi}{c+di} \cdot \frac{c-di}{c-di} = \frac{(a+bi)(c+di)}{c^2 + d^2} $ \\
+    Division $ \frac{a+bi}{c+di} $ & $ \frac{a+bi}{c+di} \cdot 1 = \frac{a+bi}{c+di} \cdot \frac{c-di}{c-di} = \frac{(a+bi)(c-di)}{c^2 + d^2} $ \\
     Modulus $|a + bi|$             & $ \sqrt{a^2 + b^2} $ \\
     $e^{i\theta} $                 & $ \cos \theta + i \sin \theta $ \\ 
     $ e^{a + bi} $                 & $ e^a \cdot e^{bi} = e^a \cos b  + i e^a \sin b $  \\
@@ -911,4 +911,4 @@
 
   \end{keysrefMultiGates}
 
-\end{document} 
+\end{document}