Update cheatsheet.fr.md

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

@@ -1419,8 +1419,11 @@ $`\quad\quad \;\; = \cdots`$
 <br>
 **$`\quad\quad\;\;=\,\theta_{moy}(\overrightarrow{r},t)\,-\,\theta_{1-2}(\overrightarrow{r},t)`$**  
 
+à terminer,
 
 
+<!--------------------
+
 $`cos\theta_1+cos\theta_2 =`$$`\;\underbrace{cos\,(\theta_{moy}+\Delta\theta_{1-2})+cos\,(\theta_{moy}-\Delta\theta_{1-2}}
 _{\color{blue}{cos(a+b)=cos\,a \,cos\,b\;-\;sin\a\,sin\,b}}`$
 
@@ -1431,7 +1434,7 @@ de même
 $`cos\theta_1-cos\theta_2 =`$$`\;\underbrace{cos\,(\theta_{moy}+\Delta\theta_{1-2})-cos\,(\theta_{moy}-\Delta\theta_{1-2}}
 _{\color{blue}{cos(a-b)=cos\,a \,cos\,b\;+\;sin\a\,sin\,b}}`$
 
-
+------->