PUMaC 2009 · 几何（A 组） · 第 1 题
PUMaC 2009 — Geometry (Division A) — Problem 1
题目详情
- A rectangular piece of paper ABCD has sides of lengths AB = 1, BC = 2. The rectangle is folded in half such that AD coincides with BC and EF is the folding line. Then fold the paper along a line BM such that the corner A falls on line EF . How large, in degrees, is ∠ ABM ?
解析
- A rectangular piece of paper ABCD has sides of lengths AB = 1, BC = 2. The rectangle is folded in half such that AD coincides with BC and EF is the folding line. Then fold the paper along a line BM such that the corner A falls on line EF . How large, in degrees, is ∠ ABM ? Solution. 30. Construct N G ⊥ BC at G . Triangles ABM , N BM , N BG are all congruent. ◦ Hence ∠ ABM = 30