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I can't see how this works . . .

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Fitness:
Ok there is this question in the itute 2006 trial exam 1. I can do part A and B ok. But I am stumped on why itute's answer is what it is for part C. It could be something obvious but I need to know what's going on with it.



Part A and B are easy. But for part C I put domain: R
Itute's answer is:


Can anyone tell me why it's \{1}? I don't see why that isn't part of the domain... Why isn't x=1 differentiable? :?

joechan521:
for that graph, y=|x^3-1|
theres a sharp turn, at where it meets the x-axis, the point(1,0)
its the pointy thing, you can see it from your graph.
at that point, you cannot find the gradient of it
hence dy/dx is not defined at x=1

Fitness:

--- Quote from: "joechan521" ---for that graph, y=|x^3-1|
theres a sharp turn, at where it meets the x-axis, the point(1,0)
its the pointy thing, you can see it from your graph.
at that point, you cannot find the gradient of it
hence dy/dx is not defined at x=1
--- End quote ---


Argh! I knew it was something simple!

Thanks heaps joechan521 :D

melanie.dee:
ah yeh i did a question like this and i was totally like wtf why, but yeh tis cos of the pointy join. whatever they're called. cusp?

Fitness:

--- Quote from: "melanie.dee" ---ah yeh i did a question like this and i was totally like wtf why, but yeh tis cos of the pointy join. whatever they're called. cusp?
--- End quote ---


Yes a cusp. The funny thing is I leaned something about this and totally forgot!  :wink:

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