Geometry and TrigonometryHardRadius from centre and a point on the circle
Geometry and Trigonometry practice question
In the xy-plane, a circle has centre (3, 4) and passes through (7, 1). What is the radius of the circle?
- A. 5Correct
- B. 25
- C. 7
- D. √7
Answer: A. 5
The radius is the distance from the centre to the point: √(4² + 3²) = √25 = 5.
Why the other answers are wrong
- B. 25
- 25 is the radius squared.
- C. 7
- 7 adds the coordinate differences (4 + 3) instead of using the distance formula.
- D. √7
- √7 uses the sum of the differences under the root.
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