AP EAMCET2002MathematicsCircle
A line is at a constant distance c from the origin and meets the coordinate axes in A and B . The locus of the centre of the circle passing through O, A, B is
Options
- Ax^2+y^2=c^2
- Bx^2+y^2=2 c^2
- Cx^2+y^2=3 c^2
- Dx^2+y^2=4 c^2
Correct answer
D. x^2+y^2=4 c^2
Step-by-step solution
Let the equation of the circle be x^2+y^2+2 g x+2 f y+c=0 It passes through origin so c=0 Then, the equation of circle is x^2+y^2+2 g x+2 f y=0 It also passes through A (x₁, 0 ) array rlrl & x₁^2+0+2 g x₁ & =0 & & g & =- x₁ 2 array It also passes through B (0, y₁ ) o+y₁^2+2 f y₁=0 f= -y₁ 2 centre of the circle is ( x₁ 2 , y₁ 2 ) Mid point of A B is ( x₁ 2 , y₁ 2 ) i.e., O M=A M=B M Thus, aligned c=O M c & = x₁^2 2 + y₁^2 2 x₁^2+y₁^2 & =4 c^2 aligned Thus, locus is x^2+y^2=4 c^2