Partial derivative

  • Thread starter teng125
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  • #1
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f(x,y)=2y / (y+cos x) .Find partial derivative w.r.t x

can someone teach me how to do this pls

thanx
 

Answers and Replies

  • #2
TD
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If y doesn't depend on x, treat y as a constant and find the derivative wrt x as you normally do.
 
  • #3
Astronuc
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To do a partial derivative with respect to one variable, treat the other variables as 'constants'. In the equation given, for a partial derivative with respect to x, treat y as a constant and use the rules for ordinary differentiation.
 
  • #4
quasar987
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Since you're doing multiple-variable calculus, you probably know how to differentiate the function f(x) = 2k / (k+cos x ) where k is a constant? Find that, then replace k by y and you get the partial derivative of f(x,y) wrt x.
 
  • #5
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can someone show this because i don't know how to do
 
  • #6
Just Differentiate f(x) as if y was a constant. Just concentrate on the x variable, the only one that is "important" now. The derivative of the function f(x) = 2k/(k+cos x ) where k is a constant (and then changing k for y) is the same as the partial derivative of f(x,y)=2y / (y+cos x) w.r.t x.
Nothing else is to be shown.
 
  • #7
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the formula is it vu'-u'v/(v^2) ??
 
  • #8
VietDao29
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teng125 said:
the formula is it vu'-u'v/(v^2) ??
Uhmm, nope. The red-highlighted part is wrong. It should read uv', i.e the whole formula is:
[tex]\left( \frac{u}{v} \right) ' = \frac{u'v - uv'}{v ^ 2}[/tex].
Can you go from here? :)
 

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