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? asked in Science & MathematicsGeography · 8 years ago

Help! About Conic Section (Circle)?

Given a circle with eq X^2 + Y^2 - 2X - 6Y + 6=0

How to prove that point (3,5) lies outside the circle?

b2-4ac>0?

1 Answer

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  • 8 years ago
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    x² + y² - 2x - 6y + 6=0,

    [(x -1)² -1]+[(y -3)² -9] -4 =0

    in the standard form

    (x -xₒ)² +(y -yₒ)² -r² =0.

    It is a circle with radius 2, centre (1, 3).

    For a point within the circle its distance to its center shouldn't exceed the radius.

    In this instance the point is (3,5). Its distance from center (1, 3) is

    d² = (3 -1)² +(5 -3)² = 8,

    d = 2√2 > 2.

    Hence the point is outside the circle.

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