English stories

\begin{aligned} & \Rightarrow \mathrm{dE}=\frac{\mathrm{Adl}}{\mathrm{r}} \cdot 2 \sin \left(\frac{\omega \mathrm{t}-\mathrm{kr}+\mathrm{k} \Delta+\omega \mathrm{t}-\mathrm{kr}-\mathrm{k} \Delta}{2}\right) \cos \left(\frac{\omega \mathrm{t}-\mathrm{kr}+\mathrm{k} \Delta-\omega \mathrm{t}+\mathrm{kr}+\mathrm{k} \Delta}{2}\right) \\ & \Rightarrow \mathrm{dE}=\frac{2 \mathrm{Adl}}{\mathrm{r}} \sin \left(\frac{2 \omega \mathrm{t}-2 \mathrm{kr}}{2}\right) \cos \left(\frac{2 \mathrm{k} \Delta}{2}\right) \\ & \Rightarrow \mathrm{dE}=\frac{2 \mathrm{Adl}}{\mathrm{r}} \sin (\omega \mathrm{t}-\mathrm{kr}) \cos (\mathrm{k} \Delta) \\ & \Rightarrow \mathrm{dE}=\frac{2 \mathrm{~A}}{\mathrm{r}} \sin (\omega \mathrm{t}-\mathrm{kr}) \cos (\mathrm{kl} \sin \theta) \mathrm{dl} As the wave eq is given by: $$ \frac{\partial^2 y}{\partial x^2}=\frac{1}{v^2}\left(\frac{\partial^2 y}{\partial x^2}\right) $$ We want to find out the solution of this equation. We know that general formula for