$\"\"$ \ \

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The ellipse equation is $\"\"$ . \ \

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consider $\"\"$ be the slope of the tangent line $\"\"$ , $\"\"$ be the slopes of the segments $\"\"$ and $\"\"$ . \ \

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Focus $\"\"$ and $\"\"$ .

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Consider the angles $\"\"$ and $\"\"$ . \ \

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Observe the figure : \ \

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$\"\"$ and $\"\"$ . \ \

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The ellipse equation is $\"\"$ . \ \

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Apply derivative on each side with respect to $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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The slope of the tangent at the point $\"\"$ .

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$\"\"$ .

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$\"\"$ be the slope of the tangent line $\"\"$ .

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$\"\"$ .

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$\"\"$

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The angles are $\"\"$ and $\"\"$ .

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Substitute $\"\"$ and $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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The ellipse $\"\"$ passes the point $\"\"$ .

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$\"\"$ .

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Susbtitute $\"\"$ in $\"\"$ .

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$\"\"$

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Substitute $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$

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Substitute $\"\"$ and $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$ \ \

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Substitute $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$ .

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Therefore, $\"\"$ .

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$\"\"$

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$\"\"$ , therefore, $\"\"$ .