Spelling typo for "cohomology"

Thanks to Brian Reinhart

tex/homology/cup-product.tex

@@ -286,7 +286,7 @@ \section{Cup products}
 	The reason is that $\alpha \smile \alpha = 0 = -(\alpha \smile \alpha)$.
 \end{example}
 
-\begin{example}[Cohmology ring of real and complex projective space]
+\begin{example}[Cohomology ring of real and complex projective space]
 	It turns out that
 	\begin{align*}
 		H^\bullet(\RP^n; \Zc2) &\cong \Zc2[\alpha]/(\alpha^{n+1}) \\