Interpolation using divided differences

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Homework Statement


Given a set of data points, derive the interpolation polynomial using divided differences.


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The Attempt at a Solution


My main question is: How am I supposed to do this if they don't give f(x)? Can I just look at the plotted data points and 'guess' the function (cos,sin,tan) that will best fit them? As a test, I tried using f(x)=cosx and graphed the resulting equation but it did not meet at the given points.
 
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One of us is very confused on this! The problem says "using divided differences". Are you saying you do not know what that is?
 
I know what it is. I'm saying that I am supposed to find the interpolation formula but they don't say what f(x). You need f(x) to calculate the divided differences.
 
No, you don't need to know f(x) but P(x) which is the interpolant polynome. They don't give f(x) but they give the value of f(x) at known points. From this, you can do the divided differences and build the P(x). All this without knowing f(x).
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...

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