Question
Find the coordinates of the foci, the vertices, the length of major axis, the minor axis, the eccentricity and the length of the latus rectum of the ellipse. $\frac{\text{x}^2}{25}+\frac{\text{y}^2}{100}=1$

Answer

The given equation is $\frac{\text{x}^2}{25}+\frac{\text{y}^2}{100}=1$ or $\frac{\text{x}^2}{5^2}+\frac{\text{y}^2}{10^2}=1$ Here, the denominator of $\frac{\text{y}^2}{100}$ is greater than the denominator of $\frac{\text{x}^2}{25}$. Therefore, the major axis is along the y-axis, while the minor axis is along the x-axis. On comparing the given equation with $\frac{\text{x}^2}{\text{b}^2}+\frac{\text{y}^2}{\text{a}^2}=1,$ we obtain b = 5 and a = 10. $\therefore \text{c}=\sqrt{\text{a}^2-\text{b}^2}=\sqrt{100-25}=\sqrt{75}=5\sqrt{3}$ Therefore, The coordinates of the foci are $(0,\pm5\sqrt{3})$ The coordinates of the vertices are $(0,\pm10)$ Length of major axis = 2a = 20 Length of minor axis = 2b = 10 Eccentricity, $\text{e}=\frac{\text{c}}{\text{a}}=\frac{5\sqrt{3}}{10}=\frac{\sqrt{3}}{2}$ Lenght of lacus rectum $=\frac{2\text{b}^2}{\text{a}}=\frac{2\times25}{10}=5$

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