Maclaurin Polynomial function

  • Thread starter chief10
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Homework Statement




I'm having a bit of trouble with this Maclaurin Series question. It should be simple enough but I can't get the answer which is given as x2. It's been a while since i've done series and my being rusty is a little annoying. Hopefully someone can help :) Consider:

f(x)=x*sin(x)

Question asks to find the Quadratic Maclaurin Polynomial for f(x).
So this is what I did. First I got the nth derivatives:

f1(x) = x*cos(x) + sin(x)
f2(x) = -x*sin(x) + cos(x) + sin(x)

P2(x): 0 + x*0 + (x^2)(0 + 1 + 0)*(1/2!)

= x2/2


I'm sure i'm doing something blatantly wrong here but I can't seem to work it out. Fresh eyes might be useful :)

Thanks a lot.
 

Answers and Replies

  • #2
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Oh no.. it was the derivative.. lol i've been racking my brain for 20 minutes staring at Taylor's Theorem thinking I made the error there.. ugh well that's embarrassing.
 

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