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Tangents are drawn to the ellipse (x^2)/...

Tangents are drawn to the ellipse `(x^2)/9 + (y^2)/5` at the end of the latus rectum. The area of the quadrilateral so formed is

A

27

B

`27/2`

C

` 27/4`

D

`27/55`

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To find the area of the quadrilateral formed by the tangents drawn to the ellipse \(\frac{x^2}{9} + \frac{y^2}{5} = 1\) at the ends of the latus rectum, we will follow these steps: ### Step 1: Identify the parameters of the ellipse The given ellipse is in the standard form \(\frac{x^2}{a^2} + \frac{y^2}{b^2} = 1\), where \(a^2 = 9\) and \(b^2 = 5\). Thus, we have: - \(a = 3\) - \(b = \sqrt{5}\) ### Step 2: Find the coordinates of the ends of the latus rectum The ends of the latus rectum for an ellipse are given by the points \((\pm ae, \frac{b^2}{a})\), where \(e\) is the eccentricity. First, we calculate the eccentricity \(e\): \[ e = \sqrt{1 - \frac{b^2}{a^2}} = \sqrt{1 - \frac{5}{9}} = \sqrt{\frac{4}{9}} = \frac{2}{3} \] Now, we can find the coordinates of the ends of the latus rectum: \[ \text{Coordinates} = \left(\pm ae, \frac{b^2}{a}\right) = \left(\pm 3 \cdot \frac{2}{3}, \frac{5}{3}\right) = \left(\pm 2, \frac{5}{3}\right) \] Thus, the points are \((2, \frac{5}{3})\) and \((-2, \frac{5}{3})\). ### Step 3: Find the equations of the tangents at these points The equation of the tangent to the ellipse at the point \((x_1, y_1)\) is given by: \[ \frac{xx_1}{a^2} + \frac{yy_1}{b^2} = 1 \] For the point \((2, \frac{5}{3})\): \[ \frac{2x}{9} + \frac{y \cdot \frac{5}{3}}{5} = 1 \] Simplifying this, we get: \[ \frac{2x}{9} + \frac{y}{3} = 1 \quad \Rightarrow \quad 2x + 3y = 9 \quad \text{(Equation 1)} \] For the point \((-2, \frac{5}{3})\): \[ \frac{-2x}{9} + \frac{y \cdot \frac{5}{3}}{5} = 1 \] Simplifying this, we get: \[ -\frac{2x}{9} + \frac{y}{3} = 1 \quad \Rightarrow \quad -2x + 3y = 9 \quad \Rightarrow \quad 2x - 3y = -9 \quad \text{(Equation 2)} \] ### Step 4: Find the points of intersection of the tangents with the axes **For Equation 1:** - **X-intercept (set \(y = 0\))**: \[ 2x = 9 \quad \Rightarrow \quad x = \frac{9}{2} \quad \Rightarrow \quad A\left(\frac{9}{2}, 0\right) \] - **Y-intercept (set \(x = 0\))**: \[ 3y = 9 \quad \Rightarrow \quad y = 3 \quad \Rightarrow \quad B(0, 3) \] **For Equation 2:** - **X-intercept (set \(y = 0\))**: \[ 2x = -9 \quad \Rightarrow \quad x = -\frac{9}{2} \quad \Rightarrow \quad C\left(-\frac{9}{2}, 0\right) \] - **Y-intercept (set \(x = 0\))**: \[ -3y = -9 \quad \Rightarrow \quad y = 3 \quad \Rightarrow \quad D(0, 3) \] ### Step 5: Calculate the area of the quadrilateral formed by points A, B, C, and D The quadrilateral is symmetric about the y-axis, and we can find the area of triangle \(AOB\) and then multiply by 2 for the total area. Area of triangle \(AOB\): \[ \text{Area} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times \frac{9}{2} \times 3 = \frac{27}{4} \] Thus, the total area of the quadrilateral is: \[ \text{Total Area} = 2 \times \frac{27}{4} = \frac{27}{2} \] ### Final Area Calculation Since we need to consider the area formed by both tangents, we multiply by 2: \[ \text{Required Area} = 4 \times \frac{27}{4} = 27 \text{ square units} \] ### Conclusion The area of the quadrilateral formed by the tangents at the ends of the latus rectum of the ellipse is \(27\) square units. ---
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