{"id":6779,"date":"2021-10-21T16:25:54","date_gmt":"2021-10-21T10:55:54","guid":{"rendered":"https:\/\/mathemerize.com\/?p=6779"},"modified":"2021-10-23T16:00:13","modified_gmt":"2021-10-23T10:30:13","slug":"the-equation-of-the-circle-through-the-points-of-intersection-of-x2-y2-1-0-x2-y2-2x-4y-1-0-and-touching-the-line-x-2y-0-is","status":"publish","type":"post","link":"https:\/\/mathemerize.com\/the-equation-of-the-circle-through-the-points-of-intersection-of-x2-y2-1-0-x2-y2-2x-4y-1-0-and-touching-the-line-x-2y-0-is\/","title":{"rendered":"The equation of the circle through the points of intersection of \\(x^2 + y^2 – 1\\) = 0, \\(x^2 + y^2 – 2x – 4y + 1\\) = 0 and touching the line x + 2y = 0, is"},"content":{"rendered":"
Family of circles is \\(x^2 + y^2 – 2x – 4y + 1\\) + \\(\\lambda\\)(\\(x^2 + y^2 – 1\\)) = 0<\/p>\n
(1 + \\(\\lambda\\))\\(x^2\\) + (1 + \\(\\lambda\\))\\(y^2\\) – 2x – 4y + (1 – \\(\\lambda\\))) = 0<\/p>\n
\\(x^2 + y^2 – {2\\over {1 + \\lambda}} x – {4\\over {1 + \\lambda}}y + {{1 – \\lambda}\\over {1 + \\lambda}}\\) = 0<\/p>\n
Centre is (\\({1\\over {1 + \\lambda}}\\), \\({2\\over {1 + \\lambda}}\\))\u00a0 and radius = \\(\\sqrt{4 + {\\lambda}^2}\\over |1 + \\lambda|\\)<\/p>\n
Since it touches the line x + 2y = 0, hence<\/p>\n
Radius = Perpendicular distance from center to the line<\/p>\n
i.e., |\\({1\\over {1 + \\lambda}} + 2{2\\over {1 + \\lambda}}\\over \\sqrt{1^2 + 2^2}\\)| = \\(\\sqrt{4 + {\\lambda}^2}\\over |1 + \\lambda|\\) \\(\\implies\\) \\(\\sqrt{5}\\) = \\(\\sqrt{4 + {\\lambda}^2}\\) \\(\\implies\\) \\(\\lambda\\) = \\(\\pm\\) 1.<\/p>\n
\\(\\lambda\\) = -1 cannot be possible in case of circle. So \\(\\lambda\\) = 1.<\/p>\n
Hence the equation of the circle is \\(x^2 + y^2 – x – 2y\\) = 0<\/p>\n
Find the equation of circle having the lines \\(x^2\\) + 2xy + 3x + 6y = 0 as its normal and having size just sufficient to contain the circle x(x \u2013 4) + y(y \u2013 3) = 0.<\/a><\/p>\n Find the equation of the normal to the circle \\(x^2 + y^2 \u2013 5x + 2y -48\\) = 0 at the point (5,6).<\/a><\/p>\n If the lines 3x-4y-7=0 and 2x-3y-5=0 are two diameters of a circle of area 49\u03c0 square units, then what is the equation of the circle?<\/a><\/p>\n The length of the diameter of the circle which touches the X-axis at the point (1,0) and passes through the point (2,3) is<\/a><\/p>\n