second derivative of a trig function
cos(xy) + x^7=y^7

Question

second derivative of a trig function
cos(xy) + x^7=y^7

precal · Answer

not sure what to do with the (xy)   I believe it is chain rule

hartnn · Answer

yeah, it is 
[cos (xy) ]' = -sin (xy) [xy]' = ....

precal · Answer

does the (xy)' go in front of the trig function (like a constant)?

hartnn · Answer

it gets multiplied with -sin xy 
and its not constant

precal · Answer

I think I need to go and read my book some more.  I have not seen this type of problem in a very long time.

hartnn · Answer

just chain rule and product rule is required here...

precal · Answer

did not mean to run off, I went to go look for my book

hartnn · Answer

no problem :)

precal · Answer

or let me write down what I think it is, stop me if I am incorrect  
I do write things in certain order just because I confuse myself otherwise

precal · Answer

-sin(xy)[y+y'x] + 7x^6=7y^6y'

precal · Answer

now I need to distribute -sin(xy) correct

hartnn · Answer

yes,
basically to isolate y'

precal · Answer

ok got it, I checked the key and my solutions match up.  Thanks  your explanation was exactly what I needed.

hartnn · Answer

you're welcome ^_^