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# second derivative of siny+cosy=x? watch

1. Can anyone help me out?

I know how to find the first but I am not sure how to continue:

The question is to find th 2nd derivative as a function of x if siny+cosy=x
2. dy/dx = 1/{cosy-siny} now differentiate again wrt x
3. Thanks, but I am really looking for a full answer and not just instructions. ^
4. (Original post by FloralEssence)
Thanks, but I am really looking for a full answer and not just instructions. ^
But people here on TSR want to help you learn not just do the work for you, that means nudging you in the right direction. I'd suggest you take the hints and try and work through it.
5. Not saying this is definitely easier, but if you're going to end up wanting an answer in terms of x, I'd be pretty tempted to start by rewriting as for suitable choices of .
6. (Original post by Zacken)
But people here on TSR want to help you learn not just do the work for you, that means nudging you in the right direction. I'd suggest you take the hints and try and work through it.
Apologies, my intentions were not to come across as unappreciative, but the truth is that I have pretty much exhausted my thought and am consistently getting very similar but different answers.

Sometimes, it is easier to see how other people work things out and then adjust your method.

Thank-you either way.
7. (Original post by FloralEssence)
Apologies, my intentions were not to come across as unappreciative, but the truth is that I have pretty much exhausted my thought and am consistently getting very similar but different answers.

Sometimes, it is easier to see how other people work things out and then adjust your method.

Thank-you either way.
If you post some working, people here can check it out for you and advise where you might be going wrong

Notwithstanding that, DFranklin's suggestion is probably a good way to get started...

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