Khan/khan-exercises — Issue #8473: Quotient rule - Correct answer shown but does not register as correct when selected
Author: KhanBugz
Created: 2011-12-12 22:11:31+00:00
State: open
Labels: chrome, other, win7

Reporter: jdeprin@gmail.com

Question: find d/dx of (e^x/cosx). rules state I can set e^x = f and cosx = g, f' = e^x, g' = -sinx. Quotient rule = (f)(g') - (g)(f')/(g)^2

result:
((e^x)(-sinx) - (cosx)(e^x))/cos^2x.

this result is shown in the answer key as an option but when selected, is counted as wrong. If you follow the hints, the eventual answer displayed is:

((e^x)(cosx)-(-sinx)(e^x))/cos^2x

The result given from hints is equivalent to the result listed as option 2 in the answer choice menu. both answers should be acceptable.

[quotient_rule.html?seed=78&problem=0](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/quotient_rule.html?seed=78&problem=0&debug)

[Answer timeline](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/quotient_rule.html?seed=78&problem=0&debug&activity=%5B%5B%22incorrect-activity%22%2C%22%5C%22%3Ccode%20style%3D%5C%5C%5C%22display%3A%20none%3B%20%5C%5C%5C%22%3E%5C%5C%5C%5Cdfrac%7B(e%5E%7Bx%7D\)(-%5C%5C%5C%5Csin%7Bx%7D\)-(%5C%5C%5C%5Ccos%7Bx%7D\)(e%5E%7Bx%7D\)%7D%7B(%5C%5C%5C%5Ccos%7Bx%7D\)%5E2%7D%3C%2Fcode%3E%5C%22%22%2C10%5D%2C%5B%22incorrect-activity%22%2C%22%5C%22%3Ccode%20style%3D%5C%5C%5C%22display%3A%20none%3B%20%5C%5C%5C%22%3E%5C%5C%5C%5Cdfrac%7B(e%5E%7Bx%7D\)(-%5C%5C%5C%5Csin%7Bx%7D\)-(%5C%5C%5C%5Ccos%7Bx%7D\)(e%5E%7Bx%7D\)%7D%7B(%5C%5C%5C%5Ccos%7Bx%7D\)%5E2%7D%3C%2Fcode%3E%5C%22%22%2C40%5D%2C%5B%22hint-activity%22%2C%220%22%2C65%5D%2C%5B%22hint-activity%22%2C%220%22%2C69%5D%2C%5B%22hint-activity%22%2C%220%22%2C71%5D%2C%5B%22hint-activity%22%2C%220%22%2C73%5D%2C%5B%22hint-activity%22%2C%220%22%2C74%5D%2C%5B%22hint-activity%22%2C%220%22%2C75%5D%5D)

["\\dfrac{(e^{x})(-\\sin{x})-(\\cos{x})(e^{x})}{(\\cos{x})^2}","\\dfrac{(e^{x})(-\\sin{x})-(\\cos{x})(e^{x})}{(\\cos{x})^2}"]

Mozilla/5.0 (Windows NT 6.1) AppleWebKit/535.2 (KHTML, like Gecko) Chrome/15.0.874.121 Safari/535.2

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