Merge pull request #858 from nature-of-code/notion-update-docs

illustration fixes

content/03_oscillation.html

@@ -22,7 +22,7 @@
 <h2 id="angles">Angles</h2>
 <p>Before going any further, I need to make sure you understand how the concept of an <strong>angle</strong> fits into creative coding in p5.js. If you have experience with p5.js, you’ve undoubtedly encountered this issue while using the <code>rotate()</code> function to rotate and spin objects. You’re most likely to be familiar with the concept of an angle as measured in <strong>degrees</strong> (see Figure 3.1).</p>
 <figure>
-  <img src="images/03_oscillation/03_oscillation_2.jpg" alt="Figure 3.1: Angles measured in degrees">
+  <img src="images/03_oscillation/03_oscillation_2.png" alt="Figure 3.1: Angles measured in degrees">
   <figcaption>Figure 3.1: Angles measured in degrees</figcaption>
 </figure>
 <div class="half-width-right">