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MathsMediumMCQ2021 · 17 Mar Shift 1

Q66.The line 2x −y + 1 = 0 is a tangent to the circle at the point (2, 5) and the centre of the circle lies on x −2y = 4. Then, the radius of the circle is: (1) 3√5 (2) 5√3 (3) 5√4 (4) 4√5

What This Question Tests

This question tests the properties of a tangent to a circle, specifically that the radius is perpendicular to the tangent at the point of contact, and uses conditions on the center to find the circle's radius.

Concepts Tested

Equation of a circleTangent property (radius perpendicular to tangent)Distance from a point to a line

Formulas Used

Equation of line: y - y1 = m(x - x1)

Distance formula for a point and a line

Slope of perpendicular lines m1 * m2 = -1

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