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A circle with center (2, 2) touches the ...

A circle with center (2, 2) touches the coordinate axes and a straight line AB where A and B ie on direction of coordinate axes such that the lies between and the line AB be the origin then the locus of circumcenter of `triangle OAB` will be:

A

`xy=x+y+sqrt(x^(2)+y^(2))`

B

`xy=x+y-sqrt(x^(2)+y^(2))`

C

`xy+x+y=sqrt(x^(2)+y^(2))`

D

`xy+x+y+sqrt(x^(2)+y^(2))=0`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the locus of the circumcenter of triangle OAB, where O is the origin, A and B are points on the axes, and the circle with center (2, 2) touches the coordinate axes. ### Step-by-step Solution: 1. **Identify the Circle and its Properties**: - The circle has a center at (2, 2) and touches the coordinate axes. Therefore, the radius of the circle is 2. - The equation of the circle can be written as: \[ (x - 2)^2 + (y - 2)^2 = 2^2 \] - Simplifying gives: \[ (x - 2)^2 + (y - 2)^2 = 4 \] 2. **Define Points A and B**: - Let point A be (A, 0) on the x-axis and point B be (0, B) on the y-axis. - The coordinates of points A and B are determined by the line AB. 3. **Find the Midpoint (Circumcenter)**: - The circumcenter of triangle OAB is the midpoint of the line segment AB. - The coordinates of the circumcenter (H, K) can be calculated as: \[ H = \frac{A + 0}{2} = \frac{A}{2}, \quad K = \frac{0 + B}{2} = \frac{B}{2} \] - Thus, the circumcenter is at: \[ \left(\frac{A}{2}, \frac{B}{2}\right) \] 4. **Use the Condition of the Circle**: - The circle touches the line AB, which means the perpendicular distance from the center of the circle (2, 2) to the line AB must equal the radius (2). - The equation of line AB can be expressed as: \[ y = -\frac{B}{A}x + B \] - The general form of the line is: \[ Ax + By - B = 0 \] 5. **Calculate the Distance from the Circle's Center to the Line**: - The distance \(d\) from the point (2, 2) to the line \(Ax + By - B = 0\) is given by: \[ d = \frac{|A(2) + B(2) - B|}{\sqrt{A^2 + B^2}} = \frac{|2A + 2B - B|}{\sqrt{A^2 + B^2}} = \frac{|2A + B|}{\sqrt{A^2 + B^2}} \] - Setting this equal to the radius (2): \[ \frac{|2A + B|}{\sqrt{A^2 + B^2}} = 2 \] 6. **Square Both Sides**: - Squaring both sides gives: \[ (2A + B)^2 = 4(A^2 + B^2) \] - Expanding and rearranging leads to: \[ 4A^2 + 4AB + B^2 = 4A^2 + 4B^2 \] - Simplifying gives: \[ 4AB + B^2 - 4B^2 = 0 \implies 4AB - 3B^2 = 0 \] - Factoring out B: \[ B(4A - 3B) = 0 \] - This gives two cases: \(B = 0\) or \(4A - 3B = 0\). 7. **Find the Locus**: - From \(4A - 3B = 0\), we can express \(B\) in terms of \(A\): \[ B = \frac{4}{3}A \] - Therefore, the locus of the circumcenter (H, K) where \(H = \frac{A}{2}\) and \(K = \frac{B}{2}\) becomes: \[ K = \frac{4}{3} \cdot \frac{A}{2} = \frac{2}{3}A \] 8. **Final Equation**: - Substituting \(A = 3K/2\) into \(H\) gives: \[ H = \frac{3K}{4} \] - Thus, the locus can be expressed as: \[ 4H = 3K \quad \text{or} \quad 3K - 4H = 0 \] ### Conclusion: The locus of the circumcenter of triangle OAB is given by the equation: \[ 3K - 4H = 0 \]
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