圆计算器
知道圆的某一个量？输入它，即可得到半径、直径、周长和面积。
结果
输入数值并点击“计算”查看结果。
公式
Circumference is the distance around the circle.
Area is the space inside the circle.
如何使用此计算器
- Choose which measurement you know and enter it.
- Press Calculate. Exact answers are given in terms of π, with decimals underneath.
例题
A circle with radius 5
Diameter = 2 × 5 = 10.
Circumference = 2π × 5 = 10π ≈ 31.415927. Area = π × 5² = 25π ≈ 78.539816.
常见问题
Why is the answer written with π?
π is irrational, so “25π” is the exact answer. The decimal below it is rounded.
What units should I use?
Any unit works. Lengths come out in the same unit; area comes out in that unit squared.