fixing typos, thanks to thisisian

book.tex

@@ -4686,9 +4686,9 @@ The \code{explicate-tail} function needs an additional case for
 \key{if}. The branches of the \key{if} inherit the current context, so
 they are in tail position.  Let $B_1$ be the result of
 \code{explicate-tail} on the ``then'' branch of the \key{if}, so $B_1$
-is a $\Tail$ AST node.  Let $B_2$ be the result of apply
+is a $\Tail$ AST node.  Let $B_2$ be the result of applying
 \code{explicate-tail} to the ``else'' branch. Finally, let $B_3$ be
-the $\Tail$ that results fromapplying \code{explicate-pred} to the
+the $\Tail$ that results from applying \code{explicate-pred} to the
 predicate $\itm{cnd}$ and the blocks $B_1$ and $B_2$.  Then the
 \key{if} as a whole translates to block $B_3$.
 \[
@@ -4707,7 +4707,7 @@ variable $x$ and then the control continues to some block $B_1$.  The
 code that we generate for both the ``then'' and ``else'' branches
 needs to continue to $B_1$, so to avoid duplicating $B_1$ we instead
 add it to the control flow graph with a fresh label $\ell_1$. The
-branches of the \key{if} inherit the current context, so that are in
+branches of the \key{if} inherit the current context, so they are in
 assignment positions.  Let $B_2$ be the result of applying
 \code{explicate-assign} to the ``then'' branch, variable $x$, and the
 block \GOTO{$\ell_1$}.  Let $B_3$ be the result of applying
@@ -5927,7 +5927,7 @@ program accesses the element in the inner tuple tuple via two vector
 references.
 % tests/s2_17.rkt
 \begin{lstlisting}
-(vector-ref (vector-ref (vector (vector 42)) 0) 0))
+(vector-ref (vector-ref (vector (vector 42)) 0) 0)
 \end{lstlisting}
 
 \section{Shrink}