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The tangents drawn from a point P to the...

The tangents drawn from a point P to the ellipse make angles ` theta_(1) and theta_(2)` with the major axis , find the locus of P when
` tan theta _(1) + tan theta _(2)` is constant (= c)

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To find the locus of the point P from which tangents are drawn to the ellipse such that the sum of the tangents' slopes (tan θ₁ + tan θ₂) is constant, we can follow these steps: ### Step-by-Step Solution: 1. **Equation of the Ellipse**: The standard form of the ellipse is given by: \[ \frac{x^2}{a^2} + \frac{y^2}{b^2} = 1 \] 2. **Equation of the Tangent**: The equation of the tangent to the ellipse at a point can be expressed as: \[ y = mx + \sqrt{a^2m^2 + b^2} \] where \( m \) is the slope of the tangent. 3. **Point P**: Let the point P be represented as \( (α, β) \). Since the tangent passes through this point, we substitute \( (α, β) \) into the tangent equation: \[ β = mα + \sqrt{a^2m^2 + b^2} \] 4. **Rearranging the Equation**: Rearranging gives: \[ β - mα = \sqrt{a^2m^2 + b^2} \] Now, squaring both sides: \[ (β - mα)^2 = a^2m^2 + b^2 \] 5. **Expanding and Rearranging**: Expanding the left side: \[ β^2 - 2mαβ + m^2α^2 = a^2m^2 + b^2 \] Rearranging gives: \[ (α^2 - a^2)m^2 - 2αβm + (β^2 - b^2) = 0 \] 6. **Using Properties of Quadratic Roots**: In this quadratic equation in terms of \( m \), let \( m_1 \) and \( m_2 \) be the roots (slopes of the tangents). According to Vieta's formulas: - The sum of the roots \( m_1 + m_2 = \frac{-(-2αβ)}{(α^2 - a^2)} = \frac{2αβ}{α^2 - a^2} \) - The product of the roots \( m_1m_2 = \frac{β^2 - b^2}{α^2 - a^2} \) 7. **Given Condition**: We know from the problem that: \[ \tan θ_1 + \tan θ_2 = c \] This implies: \[ m_1 + m_2 = c \] Therefore, we can equate: \[ \frac{2αβ}{α^2 - a^2} = c \] 8. **Final Rearrangement**: Rearranging gives: \[ 2αβ = c(α^2 - a^2) \] This can be rewritten as: \[ 2xy = cx^2 - ca^2 \] 9. **Locus Equation**: Thus, the locus of point P is given by: \[ 2xy = cx^2 - ca^2 \] ### Final Answer: The locus of point P is: \[ 2xy = cx^2 - ca^2 \]
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