proof fixes

docs/zh-CN/index.html

@@ -4471,7 +4471,7 @@ if (roots.length > 0) {
             as it turns out, there is a way to define curvature in such a way
             that it only relies on what the curve actually looks like, and given
             where this section is in the larger body of this Primer, it should
-            hopefully not be surprising that we thing we can use to define
+            hopefully not be surprising that thee thing we can use to define
             curvature is the thing we talked about in the previous section: arc
             length.
           </p>
@@ -4507,7 +4507,7 @@ if (roots.length &gt; 0) {
             integral disappears entirely (because of the
             <a
               href="https://en.wikipedia.org/wiki/Fundamental_theorem_of_calculus"
-              >fundamental therem of calculus</a
+              >fundamental theorem of calculus</a
             >), and we're left with some surprisingly simple maths that relates
             curvature (denoted as κ, "kappa") to—and this is the truly
             surprising bit—a specific combination of derivatives of our original