Issues from Github 2019.04.19

Author: jimmysong

ch01.asciidoc

@@ -505,10 +505,10 @@ include::code-ch01/answers.py[tag=exercise4,indent=0]
 
 include::code-ch01/answers.py[tag=exercise5,indent=0]
 
-.Why Fields Are Prime
+.Why Prime Fields are Useful
 [NOTE]
 ====
-The answer to Exercise 5 is why fields have to have a _prime_ power number of elements.
+The answer to Exercise 5 is why we choose to use finite fields with a _prime_ number of elements.
 No matter what _k_ you choose, as long as it's greater than 0, multiplying the entire set by _k_ will result in the same set as you started with.
 
 Intuitively, the fact that we have a prime order results in every element of a finite field being equivalent.

ch03.asciidoc

@@ -87,7 +87,7 @@ Being able to do the same equation but with different definitions for the basic
 
 We've already coded the two classes that we need to implement elliptic curve points over a finite field.
 However, to check our work, it will be useful to create a test suite.
-We will do this using the results of Exercise 2:
+We will do this using the results of Exercise 1:
 
 [source,python]
 ----

preface.asciidoc

@@ -206,7 +206,7 @@ This element signifies a general note.
 
 [WARNING]
 ====
-This element indicates a waning or caution.
+This element indicates a warning or caution.
 ====
 
 === Using Code Examples