Add schematic image for cantilever beam tutorial

Author: nikoscham

assets/cantilever-beam-1d.png

@@ -168,6 +168,15 @@ <h2 id="mathematicalformulation"><a name="Mathematical formulation"></a>Mathemat
       concentrated tip load \(P = -1000\) is applied. Since there is no distributed load along the span
       (\(q(x) = 0\)), the beam bends solely due to the point load applied at its free end.
     </p>
+
+    <div class="center-image">
+      <img src="../assets/cantilever-beam-1d.png" alt="Cantilever beam schematic" width="300" />
+      <p class="image-caption">
+        Schematic of the cantilever beam: clamped support at x=0 (w=0, &theta;=0) and a downward tip point
+        load P at x=L
+      </p>
+    </div>
+
     <p>For this problem, the deflection admits the classical closed-form analytical solution:</p>
     <p>\(w(x) = \frac{P}{6EI}\left(3Lx^2 - x^3\right)\)</p>
     <p>with the corresponding rotation:</p>