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**Redtwit** Hello, just thought i'd quickly say, I'm new here =].

I'm doing some problems on Taylors Series, like this one:

Find the Taylor polynomial of order 2 at x = a generated by the

function f(x) = sin(sin x) at a = 0:

I did this, coming to the correct answer by finding the 2 derivatives etc. The solutions however gave me this, which was a lot difference from my working:

sin(sin x) = sin x + O(sin^3 x) = x + O(x^3);

Hence P2(x) = x:

I was hoping somebody could perhaps explain the O symbol to me? and how sin(sin x) = sin c+ O(sin^3 x) etc.