Update cheatsheet.fr.md

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

@@ -1140,11 +1140,11 @@ _La superposition de deux ondes harmoniques est une onde harmonique._
 
 $`=\sqrt{\big(\overrightarrow{U}_1 + \overrightarrow{U}_2\big)\cdot\big(\overrightarrow{U}_1 + \overrightarrow{U}_2\big)}`$
 
-$`\mathbf{ =
- \sqrt{\overrightarrow{U}_1\cdot\overrightarrow{U}_1 + \overrightarrow{U}_2\cdot\overrightarrow{U}_2+2\;\overrightarrow{U}_1\cdot\overrightarrow{U}_2}}`$
+$`=\sqrt{\overrightarrow{U}_1\cdot\overrightarrow{U}_1 + \overrightarrow{U}_2\cdot\overrightarrow{U}_2+2\;\overrightarrow{U}_1\cdot\overrightarrow{U}_2}`$
 
-$`\mathbf{ =
- \sqrt{\|\overrightarrow{U}_1\|^2+ \|\overrightarrow{U}_2\|^2+2\;\|\overrightarrow{U}_1\|\;\|\overrightarrow{U}_2\|\;cos\Big(\widehat{\overrightarrow{U}_1,\overrightarrow{U}_2}\Big)}}`$
+$`=\sqrt{\|\overrightarrow{U}_1\|^2+ \|\overrightarrow{U}_2\|^2+2\;\|\overrightarrow{U}_1\|\;\|\overrightarrow{U}_2\|\;cos\Big(\widehat{\overrightarrow{U}_1,\overrightarrow{U}_2}\Big)}`$
+
+$`=\sqrt{A_1^2\;+\;A_2^2\;+\;2 \;A_1\,A_2\;cos(\theta_2-\theta_1)}`$**
 
 **$`\mathbf{ =
  \sqrt{A_1^2\;+\;A_2^2\;+\;
@@ -1158,8 +1158,6 @@ $`\mathbf{ =
 
 $`=\sqrt{(A_1\,e^{\,i\,\theta_1}+A_2\,e^{\,i\,\theta_2})\cdot(A_1\,e^{\,-i\,\theta_1}+A_2\,e^{\,-i\,\theta_2})}`$
 
-$`=\sqrt{(A_1\,e^{\,i\,\theta_1}+A_2\,e^{\,i\,\theta_2})\cdot(A_1\,e^{\,-i\,\theta_1}+A_2\,e^{\,-i\,\theta_2})}`$
-
 $`=\sqrt{A_1^2\,e^0 +A_2\,e^0 + A_1 e^{\,i\,\theta_1} A_2\,e^{\,-i\,\theta_2} + A_1 e^{\,-i\,\theta_1} A_2\,e^{\,i\,\theta_2}}`$
 
 $`=\sqrt{A_1^2 +A_2 + A_1A_2\,\big( e^{\,i\,(\theta_1 -\theta_2)} + e^{\,-i\,(\theta_1 - \theta_2}}`$