# summations

• Dec 15th 2008, 02:36 PM
holly123
summations
sorry i have two more questions..

how do i evaluate this without a calculator?
(sum from k=1 to k=5) of 1/k

and what is sigma notation? it says to write 1+2+4+8+16+32 in sigma notation

sorry i'm so lost i hate missing class!!(Headbang)
• Dec 15th 2008, 02:40 PM
euclid2
Quote:

Originally Posted by holly123
sorry i have two more questions..

how do i evaluate this without a calculator?
(sum from k=1 to k=5) of 1/k

and what is sigma notation? it says to write 1+2+4+8+18+32 in sigma notation

sorry i'm so lost i hate missing class!!(Headbang)

Should it be 16 rather then 18?
• Dec 15th 2008, 02:46 PM
holly123
yes sorry typo!
• Dec 15th 2008, 02:56 PM
euclid2
Quote:

Originally Posted by holly123
sorry i have two more questions..

how do i evaluate this without a calculator?
(sum from k=1 to k=5) of 1/k

and what is sigma notation? it says to write 1+2+4+8+16+32 in sigma notation

sorry i'm so lost i hate missing class!!(Headbang)

Note: a sigma notation is a way to write out a long sum

$\sum_{k=0}^5 2^k$ is the sigma notation for that sequence

$\sum_{k=0}^5 2^k$ $= 2^0+2^1+2^2+2^3+2^4+2^5= 1+4+8+16+32 = 63$

Does that match the book answer?
• Dec 15th 2008, 03:40 PM
holly123
yes thank you very much that makes sense
how would i do 1+1/4+1/9+1/16
would it be (1)/(x^2) from 1 to 4?
• Dec 16th 2008, 02:47 AM
Quote:

how do i evaluate this without a calculator?
(sum from k=1 to k=5) of 1/k
Find a common denominator and convert all of the fractions to it, then add up the numerators. I know it seems like you should know a better way by now, but I don't think there is one.

Quote:

how would i do 1+1/4+1/9+1/16
would it be (1)/(x^2) from 1 to 4?
exactly. Very good.
• Dec 16th 2008, 02:41 PM
holly123
thank you! im still confused on summations though.
f(x)= 1/(x+1) from [0,1] and n=2
how do i set up the summation for LRAM, RRAM, MRAM, and the trapezoidal method?