Sigma notation

  • Thread starter giant016
  • Start date
  • #1
21
0

Homework Statement


Sigma.jpg

I'm just having trouble seeing how the book is getting from point-to-point. I understand the area=height X Width part of the equation, but I don't see how in the seconds step (2i/5)(2/5) turns into [-(2i/5)^2+5](2/5). Smae goes for the second step in the second equation circled in red.
 

Answers and Replies

  • #2
jamesrc
Science Advisor
Gold Member
476
1
height is given by f(x) = f(2i/5) so you plug in x=2i/5:
[tex]f\left(\frac{2i}{5}\right)=-\left(\frac{2i}{5}\right)^2+5[/tex]

same goes for the second equation

you have an expression for x as a function of i that you plug in to find f as a function of i.
 
  • #3
21
0
Ahh, now I see. I totally forgot about the f(x)=-x^2 equation. Thanks!
 

Related Threads on Sigma notation

  • Last Post
Replies
16
Views
5K
D
  • Last Post
Replies
4
Views
1K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
6
Views
2K
  • Last Post
Replies
9
Views
2K
  • Last Post
Replies
3
Views
7K
  • Last Post
Replies
3
Views
722
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
9
Views
3K
Top