Exercise 3.5 in 3.1.2: solution added; fixes #619

Author: martin-henz

xml/chapter3/section1/subsection2.xml

@@ -591,6 +591,35 @@ function random_in_range(low, high) {
 random_in_range(80000, 81000);
       </JAVASCRIPT>
     </SNIPPET>
+    <SOLUTION>
+      <SNIPPET HIDE="yes">
+	<NAME>exercise_3_5_solution_example</NAME>
+	<JAVASCRIPT>
+function inside_unit_circle(x, y) {
+    return square(x) + square(y) &lt;= 1;
+}
+estimate_integral(inside_unit_circle, -1, 1, -1, 1, 50000);
+	</JAVASCRIPT>
+      </SNIPPET>
+      <SNIPPET>
+	<NAME>exercise_3_5_solution</NAME>
+	<REQUIRES>square_definition</REQUIRES>
+	<REQUIRES>monte_carlo</REQUIRES>
+	<EXAMPLE>exercise_3_5_solution_example</EXAMPLE>
+	<JAVASCRIPT>
+function random_in_range(low, high) {
+    const range = high - low;
+    return low + math_random() * range;
+}
+function estimate_integral(pred, x1, x2, y1, y2, trials) {
+    const area_rect = (x2 - x1) * (y2 - y1);
+    return monte_carlo(trials,
+                       () => pred(random_in_range(x1, x2),
+                                  random_in_range(y1, y2))) * area_rect;
+}
+	</JAVASCRIPT>
+      </SNIPPET>
+    </SOLUTION>
   </EXERCISE>
 
   <EXERCISE>