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Tangents are drawn from the point P(3,4)...

Tangents are drawn from the point P(3,4) to the ellipse `x^(2)/9+y^(2)/4=1` touching the ellipse at point A and B. Q. The coordinates of A and B are

A

(3,0) amd (0,2)

B

`(-8/5,(2sqrt161/15)and (-9/8,8/5)`

C

`(-8/5,(2sqrt161/15)and(0,2)`

D

`(3,0) and (-9/5,8/5)`

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To find the coordinates of the points A and B where the tangents from the point P(3, 4) touch the ellipse given by the equation \( \frac{x^2}{9} + \frac{y^2}{4} = 1 \), we will follow these steps: ### Step 1: Identify the equation of the ellipse The equation of the ellipse is given as: \[ \frac{x^2}{9} + \frac{y^2}{4} = 1 \] Here, \( a^2 = 9 \) (so \( a = 3 \)) and \( b^2 = 4 \) (so \( b = 2 \)). ### Step 2: Use the formula for the chord of contact The chord of contact from a point \( (x_1, y_1) \) to the ellipse is given by: \[ \frac{xx_1}{a^2} + \frac{yy_1}{b^2} = 1 \] Substituting \( (x_1, y_1) = (3, 4) \), \( a^2 = 9 \), and \( b^2 = 4 \): \[ \frac{3x}{9} + \frac{4y}{4} = 1 \] This simplifies to: \[ \frac{x}{3} + y = 1 \] or \[ x + 3y = 3 \quad \text{(Equation 1)} \] ### Step 3: Substitute Equation 1 into the ellipse equation Now, we will substitute \( x \) from Equation 1 into the ellipse equation. From Equation 1, we can express \( x \) as: \[ x = 3 - 3y \] Substituting this into the ellipse equation: \[ \frac{(3 - 3y)^2}{9} + \frac{y^2}{4} = 1 \] Expanding this: \[ \frac{(9 - 18y + 9y^2)}{9} + \frac{y^2}{4} = 1 \] Simplifying: \[ 1 - 2y + y^2 + \frac{y^2}{4} = 1 \] Multiplying through by 36 to eliminate the denominators: \[ 36(1 - 2y + y^2) + 9y^2 = 36 \] This simplifies to: \[ 36 - 72y + 36y^2 + 9y^2 = 36 \] Combining like terms: \[ 45y^2 - 72y = 0 \] ### Step 4: Factor the equation Factoring out \( y \): \[ y(45y - 72) = 0 \] Setting each factor to zero gives: 1. \( y = 0 \) 2. \( 45y - 72 = 0 \) → \( y = \frac{72}{45} = \frac{8}{5} \) ### Step 5: Find corresponding x-coordinates Now, we will find the corresponding x-coordinates for each y-value. 1. For \( y = 0 \): \[ x = 3 - 3(0) = 3 \] So, one point is \( A(3, 0) \). 2. For \( y = \frac{8}{5} \): \[ x = 3 - 3\left(\frac{8}{5}\right) = 3 - \frac{24}{5} = \frac{15}{5} - \frac{24}{5} = -\frac{9}{5} \] So, the second point is \( B\left(-\frac{9}{5}, \frac{8}{5}\right) \). ### Final Answer The coordinates of points A and B are: - A: \( (3, 0) \) - B: \( \left(-\frac{9}{5}, \frac{8}{5}\right) \)
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ARIHANT MATHS ENGLISH-ELLIPSE-Exercise (Questions Asked In Previous 13 Years Exam)
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