Question
Consider a point $P_{1}\left(x_{1}, y_{1}\right)$ on the ellipse $b^{2} x^{2}+a^{2} y^{2}=a^{2} b^{2}$ A tangent to the ellipse at $p_{1}$ is a line through $p_{1}$ with no other point on the ellipse. Prove that if $y_{1} \neq 0$, there is a tangent at $\mathrm{p}_{1}$, its slope is $\mathrm{m}=\left(-\mathrm{b}^{2} \mathrm{x}_{1}\right) /\left(\mathrm{a}^{2} \mathrm{y}_{1}\right)$ and its equationcan be put in the form $\mathrm{x}_{1} \mathrm{x} / \mathrm{a}^{2}+\mathrm{y}_{1} \mathrm{y} / \mathrm{b}^{2}=1$.
Step 1
First, we need to show that there exists a tangent at point $P_1$. Since $y_1 \neq 0$, we know that $P_1$ is not on the major or minor axis of the ellipse. Therefore, it is not a degenerate case, and there must exist a tangent at $P_1$. Show more…
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Key Concepts
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Show that an equation of the line tangent to the ellipse $\frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}=1$ at the point $\left(x_{0}, y_{0}\right)$ is $$\frac{x x_{0}}{a^{2}}+\frac{y y_{0}}{b^{2}}=1$$
Parametric and Polar Curves
Conic Sections
Prove: The line tangent to the ellipse $$\frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}=1$$ at the point $\left(x_{0}, y_{0}\right)$ has the equation $$\frac{x x_{0}}{a^{2}}+\frac{y y_{0}}{b^{2}}=1$$
PARAMETRIC AND POLAR CURVES; CONIC SECTIONS
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