Using rolle's theorem
f(x)=sin(5x) [ , }

Step-by-step explanation:

Hence:

f(π/5)=f(2π/5)

Rolle's Theorem:

There is at least one ξ in [π/5, 2π/5], such as: f'(ξ)=0

answer: the proof is mentioned below.

step-by-step explanation:

since, given:   lines bc = ef

prove:   lines ac > ef

          statements                                           reason

1. bc=ef                                           1. given

2. ac= ab+bc                                 2. because b is the point between the  

                                                            line segment ac

3.   ac > bc                                       3. because if a line segment is equal to

                                                          the sum of two line segments then it is

                                                          always greater then each of these

                                                          individual line segments

4. ac > ef                                         4. by equality property.