# Math question

**URL:** <https://forum.kirupa.com/t/math-question/169887>\
**Category:** flash\
**Created:** [November 20, 2005, 8:56pm UTC](https://forum.kirupa.com/t/math-question/169887 "2005-11-20T20:56:27Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![kdd](https://avatars.discourse-cdn.com/v4/letter/k/ecb155/32.png) [@kdd](https://forum.kirupa.com/u/kdd)\
**Post date:** [November 20, 2005, 8:56pm UTC](https://forum.kirupa.com/t/math-question/169887/1 "2005-11-20T20:56:27Z")

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i want to differentiate, find slope of, this equation:  
c^2 = a^2 + b^2 - 2ab\*cos C  
^ c and ^ C are different.  
you’ve probably guessed it’s law of cosine.

i can do the first part, but what about 2ab\*cos C?  
thanks in advance.