Americans have no logic?

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October 11

Americans have no logic?

我们学校离散数学期中考试最难的一道证明题：

“Prove without using truth tables that (p ^ q) v (~p ^ r) is logically equivalent to (p -> q) ^ (~p -> r)”.

花了一晚上改了220份卷子，我惊讶地发现居然没有一个人答对。突然想起某人跟我说过的一句话：“Americans have no logic.” ^_^

2:15 AM | Blog it

Comments (7)

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	Feng Qianwrote: No... Enumerating all possibilities is essentially using a truth table. That is not scalable. Oct. 12
	KaYan Taowrote: Can I proof it by enumerating all the 8 possible true/false cases? Oct. 11
	Pengfei Huangwrote: 也许很多人不入门，但是在行业中的懂门道的人就真的会很懂。 Oct. 11
	Feng Qianwrote: 就是化简吧。Step 3 有点小小的 trick。问题是许多小盆友不懂什么是证明…… (p -> q) ^ (~p -> r) =(~p v q) ^ (p v r) =(~p ^ r) v (p ^ q) v (q ^ r) =(~p ^ r) v (p ^ q) v (p ^ q ^ r) v (~p ^ q ^ r) =(~p ^ r) v (p ^ q) Oct. 11
	sha huanwrote: i don't know how to prove either:) Oct. 11
	Sai HEwrote: 貌似逻辑能力这东西在很小的时候就成形了？ Oct. 11
	Fang Yuwrote: how to prove it? Oct. 11

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