what is the formula for the area of a pyramid

this is the formula for a right rectangular pyramid $${\mathtt{A}} = {\mathtt{lw}}{\mathtt{\,\small\textbf+\,}}{{l}{\left({\frac{{\mathtt{w}}}{{\mathtt{2}}}}\right)}}^{\,{\mathtt{2}}}{\mathtt{\,\small\textbf+\,}}{{\mathtt{h}}}^{{\mathtt{2}}}{\mathtt{\,\small\textbf+\,}}{{w}{\left({\frac{{\mathtt{l}}}{{\mathtt{2}}}}\right)}}^{\,{\mathtt{2}}}{\mathtt{\,\small\textbf+\,}}{{\mathtt{h}}}^{{\mathtt{2}}}$$ put a square root where $${\frac{{\mathtt{w}}}{{\mathtt{2}}}}$$ and $${\frac{{\mathtt{1}}}{{\mathtt{2}}}}$$ is at