#Perl, 47 + 1 = 48 bytes
Run with the `-n` flag.

    say!!/^(s(in?)?|c(os?)?|t(an?)?|ln?|log?|e)+$/i

I'm not sure this regex can be golfed any further, but I'll keep trying things.

[Try it online!](https://tio.run/nexus/perl#@1@cWKmoqB@nUayRmWevaV@TrJFfDKJLNBLB/Jw8IM5Pt69J1dRW0c/8/78iOznlv27ef11fUz0DQwMA "Perl – TIO Nexus")

I downloaded a dictionary file, and the longest word I found was 11 letters -- `tattletales`