diff --git a/mathics/builtin/drawing/plot.py b/mathics/builtin/drawing/plot.py
index 0dc1e18e7..1b7a79905 100644
--- a/mathics/builtin/drawing/plot.py
+++ b/mathics/builtin/drawing/plot.py
@@ -863,8 +863,8 @@ class PieChart(_Chart):
       <li>SectorSpacing" (default Automatic)
     </ul>
 
-    A pie chart for a list of values:
-    >> PieChart[Range[4]]
+    A hypothetical comparsion between types of pets owned:
+    >> PieChart[{30, 20, 10}, ChartLabels -> {Dogs, Cats, Fish}]
      = -Graphics-
 
     A doughnut chart for a list of values:
@@ -2196,18 +2196,20 @@ def eval_f(self, f, x_value):
 
 
 class PolarPlot(_Plot):
-    """
+    u"""
     <dl>
-    <dt>'PolarPlot[$r$, {$t$, $tmin$, $tmax$}]'
-        <dd>creates a polar plot of $r$ with angle $t$ ranging from
-        $tmin$ to $tmax$.
+      <dt>'PolarPlot[$r$, {$t$, $t_min$, $t_max$}]'
+      <dd>creates a polar plot of curve with radius $r$ as a function of angle $t$ ranging from $t_min$ to $t_max$.
     </dl>
 
-    >> PolarPlot[Cos[5t], {t, 0, Pi}]
+    >> PolarPlot[Cos[5\\[Theta]], {\\[Theta], 0, Pi}]
      = -Graphics-
 
     >> PolarPlot[{1, 1 + Sin[20 t] / 5}, {t, 0, 2 Pi}]
      = -Graphics-
+
+    >> PolarPlot[Sqrt[t], {t, 0, 16 Pi}]
+     = -Graphics-
     """
 
     options = _Plot.options.copy()
diff --git a/mathics/doc/common_doc.py b/mathics/doc/common_doc.py
index 1412939ba..ad5f9c021 100644
--- a/mathics/doc/common_doc.py
+++ b/mathics/doc/common_doc.py
@@ -262,6 +262,7 @@ def repl_list(match):
             ("\u00e9", r"\'e"),
             ("\u00ea", r"\^e"),
             ("\u03b3", r"$\gamma$"),
+            ("\u03b8", r"$\theta$"),
             ("\u03bc", r"$\mu$"),
             ("\u03c0", r"$\pi$"),
             ("\u2107", r"$\mathrm{e}$"),
diff --git a/mathics/docpipeline.py b/mathics/docpipeline.py
index 464c3f395..57ecda197 100644
--- a/mathics/docpipeline.py
+++ b/mathics/docpipeline.py
@@ -85,15 +85,16 @@ def test_case(test, tests, index=0, subindex=0, quiet=False, section=None):
     def fail(why):
         part, chapter, section = tests.part, tests.chapter, tests.section
         print_and_log(
-            "%sTest failed: %s in %s / %s\n%s\n%s\n"
-            % (sep, section, part, chapter, test, why)
-        )
+            f"""{sep}Test failed: {section} in {part} / {chapter}
+{part}
+n{why}
+""".encode("utf-8"))
         return False
 
     if not quiet:
         if section:
-            print("%s %s / %s %s" % (stars, tests.chapter, section, stars))
-        print("%4d (%2d): TEST %s" % (index, subindex, test))
+            print(f"{stars} {tests.chapter} / {section} {stars}".encode("utf-8"))
+        print(f"{index:4d} ({subindex:2d}): TEST {test}".encode("utf-8"))
 
     feeder = MathicsSingleLineFeeder(test, "<test>")
     evaluation = Evaluation(definitions, catch_interrupt=False, output=TestOutput())