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Let the curve is x^2-2y^2=4 Tangent draw...

Let the curve is `x^2-2y^2=4` Tangent drawn at `P(4,sqrt6)` cuts the x-axis at R and latus rectum at `Q(x_1,y_1)(x_1 gt 0)` , F be focus nearest to P. Then `arDeltaQPF`

A

`2-sqrt6/7`

B

`2-sqrt6/2`

C

`3/2`

D

`sqrt6/2`

Text Solution

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The correct Answer is:
To solve the problem, we need to find the area of triangle QPF formed by the points Q, P, and F, where P is the point on the curve, R is the point where the tangent at P intersects the x-axis, and Q is the point on the latus rectum of the hyperbola defined by the equation \(x^2 - 2y^2 = 4\). ### Step 1: Identify the curve and its properties The given curve is \(x^2 - 2y^2 = 4\). This is a hyperbola. We can rewrite it in standard form: \[ \frac{x^2}{4} - \frac{y^2}{2} = 1 \] From this, we can identify: - The semi-major axis \(a = 2\) - The semi-minor axis \(b = \sqrt{2}\) ### Step 2: Find the focus of the hyperbola The distance of the foci from the center is given by \(c = \sqrt{a^2 + b^2}\): \[ c = \sqrt{4 + 2} = \sqrt{6} \] Thus, the foci are located at \((\pm \sqrt{6}, 0)\). ### Step 3: Determine the coordinates of point P Point \(P\) is given as \((4, \sqrt{6})\). ### Step 4: Find the equation of the tangent at point P The equation of the tangent to the hyperbola at point \((x_0, y_0)\) is given by: \[ \frac{xx_0}{4} - \frac{yy_0}{2} = 1 \] Substituting \(P(4, \sqrt{6})\): \[ \frac{4x}{4} - \frac{\sqrt{6}y}{2} = 1 \implies x - \frac{\sqrt{6}}{2}y = 1 \] ### Step 5: Find the intersection point R with the x-axis To find the intersection with the x-axis, set \(y = 0\): \[ x - 0 = 1 \implies x = 1 \] Thus, point \(R\) is \((1, 0)\). ### Step 6: Find the coordinates of point Q on the latus rectum The latus rectum of the hyperbola is given by the lines \(x = \pm 2\) (since \(2a = 4\)). We will consider the right latus rectum at \(x = 2\): Substituting \(x = 2\) into the hyperbola equation: \[ 2^2 - 2y^2 = 4 \implies 4 - 2y^2 = 4 \implies -2y^2 = 0 \implies y = 0 \] Thus, point \(Q\) is \((2, 0)\). ### Step 7: Identify the focus F nearest to P The nearest focus to point \(P(4, \sqrt{6})\) is \(F(\sqrt{6}, 0)\). ### Step 8: Calculate the area of triangle QPF The area \(A\) of triangle formed by points \(Q(2, 0)\), \(P(4, \sqrt{6})\), and \(F(\sqrt{6}, 0)\) can be calculated using the formula: \[ A = \frac{1}{2} \left| x_1(y_2 - y_3) + x_2(y_3 - y_1) + x_3(y_1 - y_2) \right| \] Substituting the coordinates: \[ A = \frac{1}{2} \left| 2(\sqrt{6} - 0) + 4(0 - 0) + \sqrt{6}(0 - \sqrt{6}) \right| \] \[ = \frac{1}{2} \left| 2\sqrt{6} - 6 \right| = \frac{1}{2} \left| 2\sqrt{6} - 6 \right| \] ### Step 9: Simplify the area expression Calculating the area: \[ A = \frac{1}{2} \left| 2\sqrt{6} - 6 \right| = \frac{1}{2} (6 - 2\sqrt{6}) \text{ (since } 2\sqrt{6} < 6 \text{)} \] Thus, the area of triangle \(QPF\) is: \[ A = 3 - \sqrt{6} \] ### Final Answer The area of triangle \(QPF\) is \(3 - \sqrt{6}\).
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