Can anyone help me with this? It's been really annoying me and I think I am just forgetting something:(adsbygoogle = window.adsbygoogle || []).push({});

Using the series expansion for cosx in powers of x find the first four non-zero terms of the corresponding series for sec x.

I get obviously that as secx is 1/cosx it is a case of division of power series but I get confused because it is 1/a power series rather than a power series/a power series so I'm not sure how to treat this.

I would really appreciate help.

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# Power series help

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