Discussion @ 1285. Thread in a Hyperspace @ Timus Online Judge

Vladimir Yakovlev (USU) Problem 1285 "Thread in a Hyperspace" has been rejudged [2] // Problem 1285. Thread in a Hyperspace 30 Apr 2018 01:04

New tests have been added to the problem which exploit a common mistake when using acos function. Hint: try to calculate acos(sqrt(3.0) * sqrt(3.0) - 4.0) in your programming language. 269 authors (58%) with accepted solutions have been challenged.

Orient Re: Problem 1285 "Thread in a Hyperspace" has been rejudged [1] // Problem 1285. Thread in a Hyperspace 3 May 2018 17:14

Why is this a mistake?

How to modify the solution to avoid the mistake? Who knows?

Orient Re: Problem 1285 "Thread in a Hyperspace" has been rejudged // Problem 1285. Thread in a Hyperspace 3 May 2018 17:24

OK, just need to add a clamp for acos' arg.

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