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krcmd1
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I am working my lonely way through Spivack's "Calculus on Manifolds." (not a registered student anywhere, alas).
On p. 23 is a set of problems involving the inner product. I believe I've got it up to d), which asks for a function f:R->R s.t. f is differentiable but |f| is not differentiable.
I believe that |f| is not differentiable for f(x)=x. (if that's wrong I have to start the book all over).
I'm having trouble seeing how to reach this conclusion from consideration of the inner product. |f|**2 = <f,f>, and for g= <f,f>, g' = <x,1> + <1,x>,
F = g**(1/2) = |f|,
and if this is ok so far, I would expect something to be wrong with the next calculation:
F' =(1/2)g**(-1/2)(g') = (1/2)(x**2)**(-1/2) (2x) = 1.
Please help me understand what I've done wrong here. thanks
Ken C
On p. 23 is a set of problems involving the inner product. I believe I've got it up to d), which asks for a function f:R->R s.t. f is differentiable but |f| is not differentiable.
I believe that |f| is not differentiable for f(x)=x. (if that's wrong I have to start the book all over).
I'm having trouble seeing how to reach this conclusion from consideration of the inner product. |f|**2 = <f,f>, and for g= <f,f>, g' = <x,1> + <1,x>,
F = g**(1/2) = |f|,
and if this is ok so far, I would expect something to be wrong with the next calculation:
F' =(1/2)g**(-1/2)(g') = (1/2)(x**2)**(-1/2) (2x) = 1.
Please help me understand what I've done wrong here. thanks
Ken C