Update cheatsheet.fr.md

12.temporary_ins/69.waves/30.n3/20.overview/cheatsheet.fr.md

@@ -60,7 +60,7 @@ $`\newcommand{\ddpt}[1]{\overset{\large\bullet\bullet}{#1}}`$
   &=\sqrt{4\,A^2 \cdot cos\Big(\dfrac{\varphi_1 - \varphi_2}{2}\Big)\,cos\Big(\dfrac{\varphi_1 - \varphi_2}{2}\Big)}
   \end{align}`$   
   <br>
-  $`\quad\quad\small{\left.\begin{align} cos(a+b)=cos(a)cos(b)-sin(a)sin(b)\\
+  $`\quad\quad\tiny{\left.\begin{align} cos(a+b)=cos(a)cos(b)-sin(a)sin(b)\\
                      cos(a-b)=cos(a)cos(b)+-sin(a)sin(b)\end{align}
                \right\}\Longrightarrow\\
         cos^2(a)=cos(a)cos(a)=\frac{1}{2}[cos(a+a)+cos(a-a)]\\