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The polar of the line 8x-2y=11 with resp...

The polar of the line 8x-2y=11 with respect to the circle `2x^(2)+2y^(2)=11` is

A

a) (4,1)

B

b) (4,-1)

C

c) (3,1)

D

d) (4,2)

Text Solution

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To find the polar of the line \(8x - 2y = 11\) with respect to the circle \(2x^2 + 2y^2 = 11\), we can follow these steps: ### Step 1: Rewrite the Circle Equation First, we simplify the equation of the circle: \[ 2x^2 + 2y^2 = 11 \implies x^2 + y^2 = \frac{11}{2} \] This is the standard form of the circle centered at the origin with radius \(\sqrt{\frac{11}{2}}\). ### Step 2: Identify the Line Equation The line equation is given as: \[ 8x - 2y = 11 \] We can rewrite this in slope-intercept form: \[ -2y = -8x + 11 \implies y = 4x - \frac{11}{2} \] ### Step 3: Find the Pole of the Line To find the pole of the line with respect to the circle, we need to express the line in a suitable form. The general form of a line is \(Ax + By + C = 0\). Here, we can rewrite the line as: \[ 8x - 2y - 11 = 0 \] Thus, \(A = 8\), \(B = -2\), and \(C = -11\). ### Step 4: Use the Polar Equation Formula The polar of a line \(Ax + By + C = 0\) with respect to the circle \(x^2 + y^2 = r^2\) is given by: \[ \frac{Ax}{r^2} + \frac{By}{r^2} + \frac{C}{r^2} = 0 \] In our case, \(r^2 = \frac{11}{2}\). Therefore, we have: \[ \frac{8x}{\frac{11}{2}} + \frac{-2y}{\frac{11}{2}} + \frac{-11}{\frac{11}{2}} = 0 \] Multiplying through by \(\frac{11}{2}\) to eliminate the denominators: \[ 8x - 2y - 11 = 0 \] ### Step 5: Find the Chord of Contact The chord of contact from the point \(P(h, k)\) to the circle is given by: \[ xh + yk = r^2 \] Substituting \(r^2 = \frac{11}{2}\): \[ xh + yk = \frac{11}{2} \] ### Step 6: Set Up the System of Equations Now we have two equations: 1. \(xh + yk = \frac{11}{2}\) (Chord of contact) 2. \(8x - 2y = 11\) (Line equation) ### Step 7: Solve for \(h\) and \(k\) From the two equations, we can set up the ratios: \[ \frac{h}{8} = \frac{k}{-2} = \frac{\frac{11}{2}}{11} \] This implies: \[ \frac{h}{8} = \frac{1}{2} \implies h = 4 \] \[ \frac{k}{-2} = \frac{1}{2} \implies k = -1 \] ### Final Result Thus, the pole of the line \(8x - 2y = 11\) with respect to the circle \(2x^2 + 2y^2 = 11\) is: \[ (h, k) = (4, -1) \] ### Conclusion The polar of the line with respect to the circle is given by the point \( (4, -1) \).
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