Chapter 9.4, Problem 15WE

To determine

To calculate: To write the equation of ellipse with given intercepts

Answer to Problem 15WE

Equation of ellipse is $\frac{x^2}{25}+\frac{y^2}{4}=1$

Explanation of Solution

Given information: Intercepts of ellipse are $x-intercept:\pm 5;y-intercept:\pm 2$

Formula Used:

Standard form of the equation of ellipse with center $\left(h,k\right)$ and major axis parallel to x-axis is:

  $\frac{{\left(x-h\right)}^2}{a^2}+\frac{{\left(y-k\right)}^2}{b^2}=1$

Where, $a=$ x-intercept, $b=$ y-intercept, $c^2=a^2-b^2$

When, $a>b$ , foci lies on x-axis and coordinates of foci are $\left(h\pm c,k\right)$

When $b>a$ , foci lies on y-axis and coordinates of foci are $\left(h,k\pm c\right)$

Calculation:

Given the intercepts of ellipse as follows:

  $\begin{array}{l}x-intercept:\pm 5\\ y-intercept:\pm 2\end{array}$

Thus,

  $\begin{array}{l}a=\pm 5\\ b=\pm 2\end{array}$

Equation of ellipse is given as follows:

  $\frac{{\left(x-h\right)}^2}{a^2}+\frac{{\left(y-k\right)}^2}{b^2}=1$ :

Substituting the values:

  $\begin{array}{l}\frac{{\left(x-0\right)}^2}{{\left(\pm 5\right)}^2}+\frac{{\left(y-0\right)}^2}{{\left(\pm 2\right)}^2}=1\\ \frac{x^2}{25}+\frac{y^2}{4}=1\end{array}$

Conclusion:

Hence, equation of ellipse is $\frac{x^2}{25}+\frac{y^2}{4}=1$