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If the parametric values of two points ...

If the parametric values of two points
A and B lying on the circle `x^(2) + y^(2) - 6x + 4y - 12 = 0 `
are `30^(@) and 60^(@)` respectively,
then find the equation of the chord
joining A and B

Text Solution

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The correct Answer is:
To find the equation of the chord joining points A and B on the circle defined by the equation \(x^2 + y^2 - 6x + 4y - 12 = 0\), we will follow these steps: ### Step 1: Rewrite the Circle Equation First, we will rewrite the given circle equation in standard form. The equation is: \[ x^2 + y^2 - 6x + 4y - 12 = 0 \] We can complete the square for the \(x\) and \(y\) terms. - For \(x^2 - 6x\), we complete the square: \[ x^2 - 6x = (x - 3)^2 - 9 \] - For \(y^2 + 4y\), we complete the square: \[ y^2 + 4y = (y + 2)^2 - 4 \] Substituting these back into the equation gives: \[ (x - 3)^2 - 9 + (y + 2)^2 - 4 - 12 = 0 \] Simplifying this: \[ (x - 3)^2 + (y + 2)^2 - 25 = 0 \] Thus, we have: \[ (x - 3)^2 + (y + 2)^2 = 25 \] This represents a circle with center \((3, -2)\) and radius \(5\). ### Step 2: Identify the Points A and B The parametric coordinates of points A and B on the circle can be expressed as: - For point A at \(30^\circ\): \[ A = (3 + 5 \cos 30^\circ, -2 + 5 \sin 30^\circ) \] - For point B at \(60^\circ\): \[ B = (3 + 5 \cos 60^\circ, -2 + 5 \sin 60^\circ) \] Calculating these: - \(\cos 30^\circ = \frac{\sqrt{3}}{2}\), \(\sin 30^\circ = \frac{1}{2}\) - \(\cos 60^\circ = \frac{1}{2}\), \(\sin 60^\circ = \frac{\sqrt{3}}{2}\) So, we have: \[ A = \left(3 + 5 \cdot \frac{\sqrt{3}}{2}, -2 + 5 \cdot \frac{1}{2}\right) = \left(3 + \frac{5\sqrt{3}}{2}, -2 + \frac{5}{2}\right) = \left(3 + \frac{5\sqrt{3}}{2}, \frac{1}{2}\right) \] \[ B = \left(3 + 5 \cdot \frac{1}{2}, -2 + 5 \cdot \frac{\sqrt{3}}{2}\right) = \left(3 + \frac{5}{2}, -2 + \frac{5\sqrt{3}}{2}\right) = \left(\frac{11}{2}, -2 + \frac{5\sqrt{3}}{2}\right) \] ### Step 3: Find the Equation of the Chord AB The equation of the chord joining points \(A\) and \(B\) can be derived using the formula: \[ \frac{x - x_1}{\cos \theta_1} = \frac{y - y_1}{\sin \theta_1} = \frac{1}{r} \] Where \(x_1, y_1\) are the coordinates of point A and \(\theta_1\) is the angle corresponding to point A. Using the values: \[ \theta_1 = 30^\circ, \quad \theta_2 = 60^\circ \] The midpoint of the chord can be calculated, and the slope can be determined to find the equation of the line. ### Step 4: Final Equation After substituting the values and simplifying, we arrive at the equation of the chord: \[ 2x + 2y - 2 - 7 - 5\sqrt{3} = 0 \] or \[ 2x + 2y - 9 - 5\sqrt{3} = 0 \]
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