Which is Greater? $\cos(\cos 1))$ vs $\cos(\cos(\cos 1)))$

  • Topic:
  • Thread starter Thread starter anemone
  • Start date Start date
Join the discussion
Registration is free. Start your own thread to ask a follow-up.
3 replies · 2K views
anemone
Gold Member
MHB
POTW Director
Messages
3,851
Reaction score
115
Determine which of the following is greater?

$\cos(\cos 1))$ or $\cos(\cos(\cos 1)))$
 
Mathematics news on Phys.org
anemone said:
Determine which of the following is greater?

$\cos(\cos 1))$ or $\cos(\cos(\cos 1)))$

we have $\cos 1 < 1$
so $\cos(\cos 1) > (\cos 1)$
so $\cos(\cos(\cos 1)) < \cos (\cos 1))$
Hence $2^{nd}$ term is larger

above is using the fact that $\cos{t} < 1 < \frac{\pi}{2}$ and for $a > b$ $\cos (a) < \cos (b) $
 
Last edited:
Just to illustrate kaliprasad's solution (from a dynamical systems perspective):
[sp]The brown curve is $y=\cos x$, the blue line is $y=x$.
View attachment 5480
[/sp]
 
Attachments
  • cos.png
    cos.png
    5 KB · Views: 151
Thanks kaliprasad for your solution! I solved it the same way you did!

A special thanks to Opalg for attaching the graph for illustration purpose! I appreciate it!