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# differentiation c4 Watch

1. hey would anyone be able to help me

i have to differentiate cos(xy)=0.5

i typed my equation in and got a differentiative of 0=-ysinxy-xsinxydy/dx which gives me the right answer but i dont know how to get to it

thanks xxx
2. (Original post by mickymouse1995)
hey would anyone be able to help me

i have to differentiate cos(xy)=0.5

i typed my equation in and got a differentiative of 0=-ysinxy-xsinxydy/dx which gives me the right answer but i dont know how to get to it

thanks xxx
This is a combination of chain rule, product rule and implicit differentiation.
Differentiate cos(STUFF) then multiply by the derivative of the stuff in the brackets.
Hint: d/dx(y) = dy/dx
3. Chain rule:

[cos(xy)]' = cos'(xy) * [xy]'

As for [xy]', product rule:

[xy]' = x'y + y'x
4. thank you i understand now xx

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