Thread: Using Maclauriw series to find first 3 terms

Hello everyone, i need some help on this question :
By using the Maclauriw series, show that the first three terms of the expansion ln[sec(2x)+tan(2x)] in powers of x are 2x + [4(x^3)]/3 + [4(x^5)]/3.
Thanks!

It will be easiest if you find the MacLaurin Series for and integrate it, since .

Originally Posted by Difficultofindtheusername

Hello everyone, i need some help on this question :
By using the Maclauriw series, show that the first three terms of the expansion ln[sec(2x)+tan(2x)] in powers of x are 2x + [4(x^3)]/3 + [4(x^5)]/3.
Thanks!

Are you saying that you do not know what the MacLaurin series is? The MacLaurin series for function f is the Taylor's series about x= 0. It's first three terms are f(0)+ f'(0)x+ f''(0)x^2/2. So the first thing you need to do is find the first and second derivatives of ln[sec(2x)+ tan(2x)] and evaluate at x= 0. Tedious, but nothing deep.

Thank you!! managed to do it