derivative

So I have the equation:
n = \frac{1}{DL} \sqrt{\frac{gT}{\pi \sigma}} where n is the frequency of the vibration of a string of diameter D, length L, with a gravity \sigma, and being stretched with a force of T. I need to differentiate with repect to D, L \sigma and T. I've done it for D and L, I'm just having trouble with \sigma and T.

So what I've got is this: \frac{dy}{dD} = \frac{1}{-LD^{2}} \sqrt{\frac{gT}{\pi \sigma}}
and \frac{dy}{dD} = \frac{1}{-DL^{2}} \sqrt{\frac{gT}{\pi \sigma}}.

Can someone help me with the other two please? Not just the answer, but an explanation. Thanks in advance.

OP here, sorry the two last ones should have been:
\frac{dn}{dD} = \frac{1}{-LD^{2}} \sqrt{\frac{gT}{\pi \sigma}} and
\frac{dn}{dL} = \frac{1}{-DL^{2}} \sqrt{\frac{gT}{\pi \sigma}}

OP here again. Never mind, I got it.

Well this thread is certainly exciting.

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>>4
What the hell is that supposed to be?

Just set the variable you are differentiating to x, the other shit to k, and use the power rule.

>>6
Yeah, I've got it but thanks.