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COMEDK · Maths · 12. Circle

What will be the equation of circle whose centre is \((1,2)\) and touches \(X\) - axis?

  1. A \(x^{2}+y^{2}-2 x-4 y+1=0\)
  2. B \(x^{2}-y^{2}+2 x+4 y+1=0\)
  3. C \(x^{2}+y^{2}+2 x-4 y-1=0\)
  4. D \(x^{2}+y^{2}+2 x+4 y-1=0\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(x^{2}+y^{2}-2 x-4 y+1=0\)

Step-by-step Solution

Detailed explanation

The centre of the circle is given as \((h, k) = (1, 2)\). Since the circle touches the X-axis, the radius \(r\) of the circle is equal to the absolute value of the y-coordinate of the centre. Thus, \(r = |k| = |2| = 2\). The standard equation of a circle with centre \((h, k)\)…