Update cheatsheet.fr.md

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

@@ -1127,9 +1127,9 @@ $`\mathbf{ =
 
 $`\mathbf{A = \sqrt{\underline{A}\,\underline{A}^*}`$
 
-$`=\sqrt{(A_1\,e^{\,i\,\theta_1}+A_2\,e^{\,i\,\theta_2})\ cdot(A_1\,e^{\,-i\,\theta_1}+A_2\,e^{\,-i\,\theta_2})}`$
+$`=\sqrt{(A_1\,e^{\,i\,\theta_1}+A_2\,e^{\,i\,\theta_2})\cdot(A_1\,e^{\,-i\,\theta_1}+A_2\,e^{\,-i\,\theta_2})}`$
 
-$`=\sqrt{(A_1\,e^{\,i\,\theta_1}+A_2\,e^{\,i\,\theta_2})\ cdot(A_1\,e^{\,-i\,\theta_1}+A_2\,e^{\,-i\,\theta_2})}`$
+$`=\sqrt{(A_1\,e^{\,i\,\theta_1}+A_2\,e^{\,i\,\theta_2})\cdot(A_1\,e^{\,-i\,\theta_1}+A_2\,e^{\,-i\,\theta_2})}`$
 
 $`=\sqrt{A_1^2\,e^0 +A_2\,e^0 + A_1 e^{\,i\,\theta_1} A_2\,e^{\,-i\,\theta_2} + A_1 e^{\,-i\,\theta_1} A_2\,e^{\,i\,\theta_2}}`$
 
@@ -1137,7 +1137,9 @@ $`=\sqrt{A_1^2 +A_2 + A_1A_2\,\big( e^{\,i\,(\theta_1 -\theta_2)} + e^{\,-i\,(\t
 
 $`=\sqrt{A_1^2 +A_2 + 2\,A_1A_2\,cos\,(\theta_1 -\theta_2)}`$
 
-
+$`\mathbf{ =
+ \sqrt{A_1^2\;+\;A_2^2\;+\;
+2 \;A_1\,A_2\;cos(\varphi_2-\varphi_1)}}`$