The ‘universal’ equation (differentials help)

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Sophhhowa
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I’ve attached my working and the question. I think it wants me to write it in terms of a, u, t etc rather than just z but I’m not sure how
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ghostwalker
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(Original post by Sophhhowa)
I’ve attached my working and the question. I think it wants me to write it in terms of a, u, t etc rather than just z but I’m not sure how

Your problem is that, although dz/du = 1/(du/dz), it does not follow that \dfrac{d^2z}{du^2}=1\left/\dfrac{d^2u}{dz^2}


You have dz/du in terms of z, differentiate that with respect to u via the chain rule.

So, d^2z/du^2 = d(dz/du)/dz x dz/du
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Sophhhowa
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(Original post by ghostwalker)
Your problem is that, although dz/du = 1/(du/dz), it does not follow that \dfrac{d^2z}{du^2}=1\left/\dfrac{d^2u}{dz^2}


You have dz/du in terms of z, differentiate that with respect to u via the chain rule.

So, d^2z/du^2 = d(dz/du)/dz x dz/du
Ahh brilliant. I’ve got it now. I’m still not sure what it’s called though?
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ghostwalker
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(Original post by Sophhhowa)
I’m still not sure what it’s called though?
Fixed point (?). Difficult to guess as your photos don't show any point. :iiam:
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Sophhhowa
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(Original post by ghostwalker)
Fixed point (?). Difficult to guess as your photos don't show any point. :iiam:
Nope if you look back at the photos it says to symbolically evaluate the 2nd deriv (which ive now done) then it just says what’s this point called
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Sophhhowa
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(Original post by ghostwalker)
Fixed point (?). Difficult to guess as your photos don't show any point. :iiam:
Nope if you look back at the photos it says to symbolically evaluate the 2nd deriv (which ive now done) then it just says what’s this point called
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RDKGames
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(Original post by Sophhhowa)
Nope if you look back at the photos it says to symbolically evaluate the 2nd deriv (which ive now done) then it just says what’s this point called
Send the link to this, otherwise it's very unclear what point they're referring to.
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