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Mathematics 8 Online
OpenStudy (anonymous):

Hi all! How do I take the derivative of this function? (attached)

OpenStudy (anonymous):

OpenStudy (anonymous):

It's making my head hurt XD

hartnn (hartnn):

use the log rules, log A/B = .... ?

hartnn (hartnn):

and \(\log \sqrt a = \log a^{1/2}= (1/2)\log a\)

OpenStudy (anonymous):

ok I'll try and work through it

OpenStudy (anonymous):

is the first step ln(a^2 - z^2)^1/2 - ln(a^2 + z^2)^1/2 ?

hartnn (hartnn):

yeah, it can be

OpenStudy (anonymous):

lol ok

hartnn (hartnn):

now use this \(\log \sqrt a = \log a^{1/2}= (1/2)\log a\)

OpenStudy (anonymous):

(1/2)ln(a^2 -z^2)-(1/2)ln(a^2 +z^2)

hartnn (hartnn):

yes, now differentiation will be easier

OpenStudy (anonymous):

derivative of lnx is 1/x

OpenStudy (anonymous):

should I do that?

hartnn (hartnn):

yes, and you;ll need chain rule too

OpenStudy (anonymous):

f'(g)*g'

hartnn (hartnn):

yes

OpenStudy (anonymous):

ok

OpenStudy (anonymous):

(1/2)(1/(a^2 -z^2))(2a-2z)-(1/2)(1/(a^2 +z^2))(2a+2z)

OpenStudy (anonymous):

is this right?

hartnn (hartnn):

'a' is constant, its derivative = 0

OpenStudy (anonymous):

aha but z is still some function, right?

hartnn (hartnn):

yes

OpenStudy (anonymous):

so, (1/2)(1/(a^2 -z^2))(-2z)-(1/2)(1/(a^2 +z^2))(2z) ?

hartnn (hartnn):

yep!

OpenStudy (anonymous):

ok so, is the first part -4z/(a^2 -z^2)

hartnn (hartnn):

yes

OpenStudy (anonymous):

overall -4z/(a^2 -z^2) -4z/(a^2 +z^2)

OpenStudy (anonymous):

?

hartnn (hartnn):

seems correct to me

OpenStudy (anonymous):

should/can I simplify further?

hartnn (hartnn):

yes, -4z can be factored, then take LCM , some terms are getting cancelled...

OpenStudy (anonymous):

least common multiple=lcm?

hartnn (hartnn):

yes

OpenStudy (anonymous):

hmm, I think if I factor it out, that should be enough

OpenStudy (anonymous):

too much time spent studying math XD

hartnn (hartnn):

but it can be further simplified...

OpenStudy (anonymous):

hmm ok

OpenStudy (anonymous):

so I assume I take (a^2 -z^2)/(a^2 -z^2)

OpenStudy (anonymous):

?

OpenStudy (anonymous):

Well, I have to afk for a bit, then work on this some more. Thanks again as always! :)

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