Determine Expression

Write a program (using a loop) the dertimes the expression: sqrt 12 Sigma (m on top) (n=0 on bottom) ((-1/3)^n) / (2*n+1) Run the program with m=5 m=10 and m=20. Compare the results with pi (Use Long format).

this is what I have done

format long 
S=0 m=input('Input a value for m=') 
    for n=0:m S(1:m)=sqrt(12)*(S+((-1/3)^n)/(2*n+1))
end

not sure if this is right

run program for m=5 m=10 m= 20

my results m =

     5s =

Columns 1 through 4
   3.464101615137754   3.464101615137754   3.464101615137754   3.464101615137754Column 5
   3.464101615137754s =

Columns 1 through 4
11.615099820540248  11.615099820540248  11.615099820540248  11.615099820540248
Column 5
11.615099820540248
s =

Columns 1 through 4
40.312866084211663  40.312866084211663  40.312866084211663  40.312866084211663
Column 5
40.312866084211663
s =

1.0e+002 *
Columns 1 through 4
   1.396295359331753   1.396295359331753   1.396295359331753   1.396295359331753Column 5
   1.396295359331753s =

1.0e+002 *
Columns 1 through 4
   4.836956528011152   4.836956528011152   4.836956528011152   4.836956528011152Column 5
   4.836956528011152s =

1.0e+003 *
Columns 1 through 4
   1.675569596143254   1.675569596143254   1.675569596143254   1.675569596143254Column 5
   1.675569596143254

Answer 1

[bym]

the multiplication of sqrt(12) should occur outside the loop. Also do not include S in the summation:

for n = 0:m
s(n+1) = (-1/3)^n/(2*n+1);
end

now you have a vector of values you can sum & multiply by sqrt(12)

[Bobby]

Thank you

Answer 2

[Jan]

Could we have an idea?

Do you have a computer? Is Matlab installed? Did you read the getting started chapters already? Do you know, what a loop is, especially a FOR loop? Have you aksed Google for some details already?

You've posted the homework question and we cannot post the running code. So what kind of help do you expect?

[Sven]

We already have the question. We *don't* have any idea what you've tried so far. You say "I have no idea where to start". Please start by answering the following:

1. Do you have MATLAB installed?

2. Have you read the "Getting Started" chapter? (it's a *great* place to start)

3. Do you know how to write a "for loop"?

4. Please show us your "for loop" for this question and describe what you want it to do.

[Bobby]

this is what I have done

format long

S=0

m=input('Input a value for m=')

for n=0:m

S(1:m)=sqrt(12)*(S+((-1/3)^n)/(2*n+1))

end

not sure if this is right

[Sven]

Bobby, please stop deleting your comments.

[Bobby]

is my for loop correct? What about my results?

[Sean de Wolski]

Are your results correct? Do they meet the constraints of the problem? If they do, I would hazard a guess they're correct!

[Walter Roberson]

Your loop is wrong, and your results are wrong.

Re-read the question. How many elements are output from a summation ? How many output elements do you have?

Answer 3

[Wayne King]

Have you read the MATLAB Getting Started Guide? There are plenty of examples on using loops.

[Bobby]

this is what I have done

format long

S=0

m=input('Input a value for m=')

for n=0:m

S(1:m)=sqrt(12)*(S+((-1/3)^n)/(2*n+1))

end

not sure if this is right