Added taylor_term for sec(x)

Added taylor_term for sec(x).
Added unit tests corresponding to it.

Reference terms can be found here[1][2]

[1]https://www.efunda.com/math/taylor_series/trig.cfm
[2]https://en.wikipedia.org/wiki/Taylor_series

Updated variable usage, fixed formatting

Removed the declarations from the function call.
Added newline at the end.
Space after `,`

Added @cacheit. Fixed comments

Added @cacheit decorater.
Added space after `#` in comment.
Merge pull request #7300 from sushant-hiray/trig_taylor_term

Added taylor_term for sec(x)