A continuously differentiable function $ f $ since $ (0.1) $ to $ (0.1) $ has the properties

(a) f (0) = f (1) = 0.

(yes) $ f ^ & # 39;} (x) $ It is a non-increasing function of x.

Prove that the arc length of the graph does not exceed 3.

As I understand the question we want to show that $ int_ {0} 1 {f} x dx <3 $.

The first property that gives the conditions of Rolle's theorem implies that $ f ^ & # 39;} (c) = 0 $, $ c in (0,1) $.

The second property gives the hint of the maximum value existing in $ c $.

I tried to use the first theorem of the average value of integral, but found no conclusion.

Is there any other technique to solve this question?