If â–³PAB is right angle at P, where A(2,3) and B(5,7), then which of the following is/are correct?
A
Equation of circumcircle of △PAB is x2+y2−7x−10y+31=0
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B
Maximum possible area of △PAB is 254 sq. units.
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C
When area of △PAB is 6 sq. units, then there are 4 possible values of P.
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D
When area of △PAB is 6 sq. units, then there are 2 possible values of P.
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Solution
The correct options are A Equation of circumcircle of △PAB is x2+y2−7x−10y+31=0 B Maximum possible area of △PAB is 254 sq. units. C When area of △PAB is 6 sq. units, then there are 4 possible values of P. Assuming AB as a diameter of a circle, then P lies on the circle and △PAB is right angle at P
Equation of circumcircle of △PAB is (x−2)(x−5)+(y−3)(y−7)=0⇒x2+y2−7x−10y+31=0
Length of AB d=√32+42=5⇒r=52
Area of △PAB =12×PC×2r=PC×r Maximum possible area occur when PC=r, =r2=254sq. units
When area of △PAB is 6 sq. units, then 6=PC×r⇒PC=125<r Therefore, there are 4 possible values of P as seen by the figure, two above and two below.