Average value and RMS value

Hello, I am trying to verify functions taking the average and RMS value using trapz function,but I am not getting the right answer in matlab. according to the theory in the book the average value of a function is obtained by: 1/(b-a)∫〖5sin(t)〗, across the interval a<t<b. This is what I have done:

EDITOR:
%Verify  that the average value for F(t)=5sin(t), is zero.
%Verify that the RMS value for F(t)=5sin(t), is 3.535.
function z= myfun2(t)
a = 1;
b = 3; 
z =(1/b-a)*(5*sin(t)); %function for average value.
end

COMMAND WINDOW:
>> t = linspace(1,3,400);
>> z = myfun2(t);
>> average = trapz(t,z)

average =

     -5.1010

When I do it by hand, I do get zero for the average value, but in matlab and dont get zero. Is something wrong in my z function?

Answer 1

[Star Strider]

I’m guessing at what your problem actually says, but the problem may be the ‘a’ and ‘b’ limits. Adding pi to them as a factor, and correcting the definition of mean value:

myfun2 = @(t) 5*sin(t);
a =   pi;
b = 3*pi;
t = linspace(a,b,400);
z = myfun2(t);
average = trapz(t,z)./(b-a)

produces:

average =

     -95.6651e-018

which is essentially zero to floating-point precision.

The mean value is Integral(f(t),a,b)/(b-a).