Question

如图矩形abcd中ab 4cm在矩形abcd中,ab=4cm,ad=12cm,点p在ad边上以每秒1cm的速度从点a向点

Answer 1

连 BE.

设 AE = x,则 DE = 8-x.

由勾股定理：BE? = AB? AE? = 36 x?.

而 EF 是折痕,所以 BE = DE,因此有 36 x? = (8-x)?,解得 x = 7/4,从而 BE = 25/4.

设 BD 与 EF 交于点O,因为 BD 是对角线,容易算出 BD = 10,BO = 5,因此再由勾股定理可知 EO? = BE?-BO?,所以 OE = 15/4,因此 EF = 2OE = 15/2.