如何得出面积

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   1
   找出一边长。 四条边长都一样，所有的边长都是你找的这个数值。
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   2
   求边长平方。 得到面积。

   • 这么算是因为正方形就是特殊的长方形，高和底边都相等。因此用k=b*h ，b和h都是相等的值。所以也就相当于把一个数求平方得面积。
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   1
   让一边作为底边。 得出其长度。
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   2
   从上底到下底，画条垂直线，其长度即高度。

   • 如果底边不够长，不能碰到垂直线的话，就延长一下底边，直到和垂直线相交为止。
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   3
   把底边和高度带入k=b*h。

   • 要了解更多说明信息，请参阅我们的《如何得到平行四边形面积》文章。
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   1
   得出上下两底边的长度。 设为a、b。
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   2
   找出高度。 画条垂直线，和上下两底相垂直。中间线段的长度就是高的长。（h）
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   3
   把这些值代入A=0.5(a+b)h。

   • 要了解更多说明信息，请参阅我们的《如何得到梯形面积》文章。
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   1
   找出底边长和高度。 即设一条边为底边，相对点到这条边的垂直距离就是高度。
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   2
   要找面积，就把高和底代入A=0.5b*h

   • 要了解更多说明信息，请参阅我们的《如何得到三角形面积》文章。
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   1
   找出边长，以及边心距（中心点到各边的垂直距离）。 设边心距为a。
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   2
   边长乘以边数，得到周长（p）
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   3
   代入A=0.5a*p

   • 要了解更多说明信息，请参阅我们的《如何得到多边形面积》文章。
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   1
   得到半径（r）。 即圆心到圆周一点的距离。根据圆的定义，无论取哪一点，半径都是一样的。
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   2
   半径代入A=πr ²

   • 要了解更多说明信息，请参阅我们的《如何得到圆形面积》文章。
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   1
   通过上面给出的公式 k=b*h（算长方形面积），找出每侧边面的面积。
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   2
   通过对应多边形面积的计算公式，找出基底面积
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   3
   把所有面积加起来：两个全等的基底和侧边面积。 基底面积是相等的，所以直接把基底面积乘2即可。

   • 要了解更多说明信息，请参阅我们的《如何得到棱柱的表面积》文章。
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   1
   得出其中一个底圆的半径。
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   2
   找出高度。
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   3
   通过圆形面积公式找出基底面积， A=πr ²
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   4
   通过高度乘以底面周长，得出侧面积。 周长是P=2πr 因此侧面积是 A=2πhr 。
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   5
   把面积加起来。 两个全等的底面圆和侧面积加起来即可，得到总表面积 SA=2πr ² +2πhr

   • 要了解更多说明信息，请参阅我们的《如何得到圆柱体表面积》文章。
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想要得出函数曲线和x轴之间的距离？假设这个曲线的函数是f(x) ，定义域是 [a,b] 。这个部分需要积分学的相关知识。如果你还没上过积分课，读这篇时你可能会觉得一头雾水。

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   1
   用 f(x)定义关于x的函数。
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   2
   求出f(x) 在 [a,b] 内的积分。 根据微积分基本定理，如 F(x)=∫f(x) ，∫abf(x) = F(b)—F(a)。
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   3
   把a和b的值代入积分表达式。 f(x) 中，在[a,b]内的面积就是 ∫abf(x)，因此 A=F(b)—F(a)
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