Show thatf(x)g(x)dx=2f(x)g(x) are defined as f(x)=f(x-a) and g(x)+g(a-x)=4

Since,  ……..(i)  and   ………(ii)

Let I =  ……….(iii)

 I = 

=  [From eq. (i)] ……….(iv)

Adding eq. (iii) and (iv)

2I = 

= 

 2I = 

[From eq. (ii)]

 2I = 

 I =