maybe fix summary tag usage

mechanical/mmme1026_maths_for_engineering.md

@@ -40,8 +40,13 @@ $$\bar{z} = z -iy$$
 
 - Multiply numerator and denominator by the conjugate of the denominator
 
+<details>
+<summary>
+
 #### Example
 
+</summary>
+
 > \begin{align*}
   z_1 &= 5 + i \\
   z_2 &= 1 -i \\
@@ -51,6 +56,8 @@ $$\bar{z} = z -iy$$
     &= \frac{4 + 6i}{2} = 2 + 3i
 > \end{align*}
 
+</details>
+
 ### Algebra and Conjugation
 
 When taking complex conjugate of an algebraic expresion, we can replace $i$ by $-i$ before or after
@@ -148,6 +155,7 @@ $$e^{i\theta} = \cos\theta + i\sin\theta$$
 
 <details>
 <summary>
+
 ### Example 1
 
 Write $z = -1 + i$ in exponential form
@@ -163,6 +171,7 @@ Write $z = -1 + i$ in exponential form
 
 <details>
 <summary>
+
 ### Example 2
 
 The equations for a mechanical vibration problem are found to have the following mathematical
@@ -257,6 +266,7 @@ r^n(\cos\theta +i\sin\theta)^n &= r^n(\cos{n\theta} + i\sin{n\theta}) \\
 
 <details>
 <summary>
+
 ### Example 1
 
 Write $1+i$ in polar form and use de Moivre's theorem to calculate $(1+i)^{15}$.
@@ -278,6 +288,7 @@ Write $1+i$ in polar form and use de Moivre's theorem to calculate $(1+i)^{15}$.
 
 <details>
 <summary>
+
 ### Example 2
 
 Use de Moivre's theorem to show that
@@ -302,6 +313,7 @@ Use de Moivre's theorem to show that
 
 <details>
 <summary>
+
 ### Example 3
 
 Given that $n \in \mathbb{N}$ and $\omega = -1 + i$, show that
@@ -325,6 +337,7 @@ $w^n + \bar{w}^n = 2^{\frac n 2 + 1}\cos{\frac{3n\pi} 4}$ with Euler's formula.
 
 <details>
 <summary>
+
 ### Example
 
 Find which complex numbers $z$ satisfy