Hi
I think I understand the Mean Value Theorem but the question is "show that cos x >+ 1-x if x>= 0"
I just don't know where to start or what to do without 2 numbers.
Please guide me.
Thanks
a frustrated Calculus beginner
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Hi
I think I understand the Mean Value Theorem but the question is "show that cos x >+ 1-x if x>= 0"
I just don't know where to start or what to do without 2 numbers.
Please guide me.
Thanks
a frustrated Calculus beginner
Using derivatives:
You consider $\displaystyle f(x)=\cos x +x-1$ the $\displaystyle f'(x)=-\sin x+1>0$ hence the function is crescente, if $\displaystyle
x > 0 \Rightarrow f(x) > f(0)
$ I mean: $\displaystyle \cos x +x-1>cos0 +0-1=0$ $\displaystyle
\Leftrightarrow \cos x > 1 - x
$
The statement is wrong, of course; at $\displaystyle x=0$ we do have equality, whereat $\displaystyle \cos x\ge1-x$ holds for all $\displaystyle x\ge0.$