* Nous obtenons l'**expression finale** de l'onde résultante de la *superposition de deux OPPH* quelconques :
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**$`U(\overrightarrow{r},t)`$**
**$`\underline{U}(\overrightarrow{r},t)`$**
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*$`\begin{array}\quad = &A_1\,cos\big(\underbrace{\omega_1 t + \overrightarrow{k}_1\cdot\overrightarrow{r}+\varphi_1}_{\color{blue}{\theta_1(\vec{r},t)}}\big)\\
&+ \;A_2\,cos\big(\underbrace{\omega_2 t + \overrightarrow{k}_2\cdot\overrightarrow{r}+\varphi_2}_{\color{blue}{\theta_2(\vec{r},t)}}\big)
\end{array}`$*
$`\begin{array}\quad = &A_1\,exp\big[\,i\,\big(\underbrace{\omega_1 t + \overrightarrow{k}_1\cdot\overrightarrow{r}+\varphi_1}_{\color{blue}{\theta_1(\vec{r},t)}}\big)\big]\\
&+ A_2\,exp\big[\,i\,\big(\underbrace{\omega_2 t + \overrightarrow{k}_2\cdot\overrightarrow{r}+\varphi_2}_{\color{blue}{\theta_2(\vec{r},t)}}\big)\big]\end{array}`$