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October 8th, 2017, 05:09 AM  #1 
Newbie Joined: Oct 2017 From: Sweden Posts: 1 Thanks: 0  Arctan continuous, differentiable?
Hi! Can someone help me with this? I saw some examples with a sinefunction but I have no idea how to do it with arctan? Let f be the function given by: f(x)=sum(arctan(kx)/k^2) (k=1, infinity) for any x ∈ R a) Show that f is continuous for x ∈ R b) Show that f is differentiable for x not equal to 0 c) Show that f is not differentiable for x = 0 Last edited by skipjack; October 8th, 2017 at 08:02 AM. 

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arctan, continuous, differentiable 
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