Khan/khan-exercises — Issue #13671: Trigonometry challenge - more than one possible answers
Author: KhanBugz
Created: 2012-02-12 13:08:42+00:00
State: open
Labels: firefox, other

Reporter: zamfi@mail.bg

In this math problem the answer the form accepted was -1/4 pi but I answered 3/4 pi and I'm absolutely sure I'm not wrong. That is because tan is periodic with a period of pi radians, so in this case tan(3/4 pi) is equal to tan(-1/4 pi). Even more confusing is the fact that the note under the problem shows that you can give answers greater than pi/2 and actually the note itself gives the answer.

[trigonometry_challenge.html?seed=186&problem=8 (inverse_trig_functions)](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/trigonometry_challenge.html?seed=186&problem=8&debug)

[Answer timeline](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/trigonometry_challenge.html?seed=186&problem=8&debug&activity=%5B%5B%22incorrect-activity%22%2C%22%5C%223%2F4%20pi%5C%22%22%2C98%5D%2C%5B%22hint-activity%22%2C%220%22%2C3%5D%2C%5B%22hint-activity%22%2C%220%22%2C16%5D%2C%5B%22hint-activity%22%2C%220%22%2C20%5D%2C%5B%22hint-activity%22%2C%220%22%2C22%5D%2C%5B%22correct-activity%22%2C%22%5C%22-1%2F4%20pi%5C%22%22%2C45%5D%5D)

["3/4 pi","-1/4 pi"]

Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:10.0) Gecko/20100101 Firefox/10.0

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