Geometry and TrigonometryMediumMissing coordinate of a point on a circle
Geometry and Trigonometry practice question
The point (x, 4) lies on the circle x² + y² = 25 in the xy-plane, and x > 0. What is the value of x?
Answer: 3
Substitute y = 4: x² + 16 = 25, so x² = 9 and x = 3 (positive).
Common wrong answers
- If you answered 5
- 5 is the radius, which would only be the x-coordinate if y were 0.
- If you answered 9
- 9 is x², one step short.
- If you answered 21
- 21 is 25 − 4, subtracting y instead of y².
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