2019 AMC 8 第 4 题
先试着解答 2019 AMC 8 第 4 题，然后核对你的答案与视频与精心整理的解答，解答来自 LIVE by Po-Shen Loh。你也可以参加完整限时模拟考试、查看全部 2019 AMC 8 解答，或核对答案。
所有题目均经美国数学协会（MAA）官方合法授权使用。
4.
四边形 是一个周长为 米的菱形。对角线 的长度为 米。菱形 的面积是多少平方米？
Quadrilateral is a rhombus with perimeter meters. The length of diagonal is meters. What is the area in square meters of rhombus
小提示：
菱形每条边长是
Each rhombus side is
大提示：
菱形的两条对角线互相垂直且互相平分
The diagonals of a rhombus are perpendicular and bisect each other
视频讲解：
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文字解答：
可以把菱形分成 个如图所示的直角三角形。
我们知道这是直角三角形，因为菱形的两条对角线互相垂直；斜边长为 。
用勾股定理，另一条直角边长为
因此菱形面积为 正确答案是 D。
We can split the rhombus up into triangles, each of which looks like this.
We know that this is a right triangle, since the diagonals of a rhombus are perpendicular, and we know the hypotenuse is
Using the Pythagorean theorem, we get the other leg to be
This means that the area of the rhombus is Thus, the correct answer is D.
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