Study of the ellipse

Considering the ellipse with focal semidistance $4$ and cutting point with the axis $OX$ $(5, 0)$, calculate its eccentricity.

The focal semidistance is $4$ since $F$ is at $4$ from the center.

The biggest axis goes from $-5$ to $5$, therefore it measures $10$.

This way, the biggest semiaxis will be half, which is $5$.

The eccentricity will be: $e=\dfrac{c}{a}=\dfrac{4}{5}$.

$$e=\dfrac{4}{5}$$

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