# Mean Value Theorem Problem

1. Oct 2, 2007

### dontdisturbmycircles

1. The problem statement, all variables and given/known data
Show that sin x < x for all x > 0

3. The attempt at a solution
I thought I was pretty good at calculus so I have kinda been shifting my calc class onto the bottom of my todo list, but this mean value theorem problem is giving me some problems.

For x > 1, sin x $$\leq$$ 1 < x

This was my start.... after about 25 minutes of thinking about how the mean value theorem could be applied I looked in the back.. (with much reluctance, trust me). They chose 2pi instead of 1 for the first part, that is likely significant but I am not getting thepoint. They then proceed to prove that (sinx)/(x) = cos(c) for some c in (0,2pi) and I can see that at that point c sin x< x since cos(c)$$\leq 1$$ but ONLY at that point c... I don't see how it proves it for the general case in that interval...

Last edited: Oct 2, 2007
2. Oct 2, 2007

### NateTG

Can you show that the slope of the tangent of $\sin(x)$ is less than one for $0<x \leq 1$?

Then, if you assume that there is a point with $x>0,x=\sin(x)$ what happens when you apply the mean value theorem?