0\\\\x^2+y^2=e^4\; \; \to \; \; r^2=e^4,\; \; r=e^2>0\\\\S=\iint r\, dr\, d\phi=4\int_0^{\frac{\pi}{2}}d\phi\int _{e}^{e^2}r\, dr=4\int_0^{\frac{\pi}{2}}(\frac{r^2}{2}}|_e^{e^2})d\phi =\\\\=4\cdot \frac{1}{2}\int _0^{\frac{\pi}{2}}(e^4-e^2)d\phi =2(e^4-e^2)\cdot \phi |_0^{\frac{\pi}{2}}=\\\\=2(e^4-e^2)(\frac{\pi}{2}-0)=\pi e^2(e^2-1)" alt="x^2+y^2=e^2\; \; \to \; \; r^2cos^2\phi +r^2sin^2\phi=e^2,\\\\r^2(cos^2\phi +cos^2\phi )=e^2,\; \; r^2=e^2,\; r=e>0\\\\x^2+y^2=e^4\; \; \to \; \; r^2=e^4,\; \; r=e^2>0\\\\S=\iint r\, dr\, d\phi=4\int_0^{\frac{\pi}{2}}d\phi\int _{e}^{e^2}r\, dr=4\int_0^{\frac{\pi}{2}}(\frac{r^2}{2}}|_e^{e^2})d\phi =\\\\=4\cdot \frac{1}{2}\int _0^{\frac{\pi}{2}}(e^4-e^2)d\phi =2(e^4-e^2)\cdot \phi |_0^{\frac{\pi}{2}}=\\\\=2(e^4-e^2)(\frac{\pi}{2}-0)=\pi e^2(e^2-1)" align="absmiddle" class="latex-formula">
Заданная область - кольцо между окружностями с центром в (0,0) и
радиусами
