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Show that the line (x – 2) cosθ + (y – 2) sinθ = 1 touches a circle for all values of θ. Find the circle. |
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Answer» Since the line (x – 2) cosθ + (y – 2) sinθ = 1 .......(1) touches a circle so it is a tangent equation to a circle. Equation of tangent to a circle at (x1 ,y1 ) is (x – h)x1 +(y – k)y1 = a2 to a circle (x – y)2 + (y – k)2 = a2 comparing (1) and (2) we get x – h = x – 2 y – k = y – 2 and a2 = 1 x1 = 1cosθ y1 = 1sinθ ∴ Required equation of circle is (x – 2)2 + (y – 2)2 = 1 x2 + y2 – 4x – 4y + 7 = 0 |
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