Geometry and TrigonometryEasy–MediumLowest point on a circle from its equation
Geometry and Trigonometry practice question
In the xy-plane, a circle has the equation (x − 1)² + (y + 4)² = 36. What is the y-coordinate of the lowest point on the circle?
Answer: -10
The centre is (1, −4) and the radius is 6, so the lowest point is at y = −4 − 6 = −10.
Common wrong answers
- If you answered 2
- 2 is the highest point's y-coordinate.
- If you answered -40
- −40 subtracts 36 instead of the radius 6.
- If you answered -3
- −3 uses the y-coordinate of the centre with the wrong sign and no radius.
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