The radius of the circle circumscribing the quadrilateral formed by the lines 7x+y−57=0,4x−3y−29=0,7x+y−7=0 and 3x+4y−3=0 in order is
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Solution
Let the equation of the circumcircie of the quadrilateral be (7x+y−57)(7x+y−7)+λ(4x−3y−29)(3x+4y−3)=0 ∴ coefficient of x2= coefficient of y2 ⇒49+12λ=1−12λ⇒λ=−2 ∴ equation (1) becomes 25 (x2+y2)−250x+150y+225=0 i.e., x2+y2−10x+6y+9=0 Hence the radius =√52+(−3)2−9=5