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Geometry and TrigonometryMediumAnother point on the same circle

Geometry and Trigonometry practice question

In the xy-plane, a circle is centred at the origin and passes through the point (5, 12). Which of the following points also lies on the circle?

  1. A. (13, 0)Correct
  2. B. (12, 12)
  3. C. (5, 5)
  4. D. (0, 5)

Answer: A. (13, 0)

The radius is the distance from the origin to (5, 12): √(25 + 144) = 13. Any point 13 units from the origin is on the circle, and (13, 0) is exactly 13 units away.

Why the other answers are wrong

B. (12, 12)
(12, 12) is √288 ≈ 17 units from the origin — outside the circle.
C. (5, 5)
(5, 5) is √50 ≈ 7 units away — inside.
D. (0, 5)
(0, 5) is 5 units away — inside.

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