The extremities of a diameter of a circle are (1, 2) and (3, 4). Determine the equations of tangents which are parallel to this diameter.
The equation of the circle is or
Centre is
Slope of the diameter joining (1,2) and (3,4) is
Hence any line parallel to this diameter is y = x + c or x – y + c = 0
If it is a tangent, then perpendicular from centre (2,3) is equal to the radius
Hence the tangents are y = x + 3, and y = x – 1
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