知道圆周长怎么算面积 知道圆的周长怎么求面积，或知道圆的面积怎么求周长
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所以，圆的半径=周长÷2÷π
这样，就可以求出圆的半径，再根据圆的面积公式求出面积。
例如，圆的周长是25.12分米，求这个圆的面积。
25.12÷2÷3.14=4（分米）
3.14×4²=50.24（平方分米）
这个圆的面积是50.24平方分米。
知道长怎么算面积
圆周长=2x拍x半径；直径x拍
拍=3.1416
圆面积=拍x半径x半径
先从圆周算出半径，再求圆面积
圆的周长C=2πr，已知C，可以求出r=C/2π，圆的面积S=πr²=π(C/2π)²=C²/4π。
周长c=2丌r，那么由周长可以算出半径，再有面积公式s求出面积的大小。
根据周长算出半径，周长除以3.14除以2,再由半径，算面积，也就是半径的平方乘以3.14即可
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