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### AuthorTopic: I can't see how this works . . .  (Read 747 times) Tweet Share

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#### Fitness

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##### I can't see how this works . . .
« on: November 07, 2007, 08:15:23 pm »
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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

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? :?
In 2006 Fitness played: IT - Processing and Management (32).
In 2007 Fitness played: English (28), Specialist Maths (25), Math Methods (32), Multimedia, Software Development (31).
In 2008 Fitness is playing: Computer and Mathematical sciences at Victoria University.

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#### joechan521

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##### I can't see how this works . . .
« Reply #1 on: November 07, 2007, 08:20:54 pm »
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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
06 method47 chinese 2nd language advanced39
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07 ENTER 99.15

#### Fitness

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##### I can't see how this works . . .
« Reply #2 on: November 07, 2007, 08:24:15 pm »
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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

Argh! I knew it was something simple!

Thanks heaps joechan521
In 2006 Fitness played: IT - Processing and Management (32).
In 2007 Fitness played: English (28), Specialist Maths (25), Math Methods (32), Multimedia, Software Development (31).
In 2008 Fitness is playing: Computer and Mathematical sciences at Victoria University.

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#### melanie.dee

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##### I can't see how this works . . .
« Reply #3 on: November 07, 2007, 08:24:20 pm »
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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

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##### I can't see how this works . . .
« Reply #4 on: November 07, 2007, 08:26:55 pm »
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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?