Array Formula for a Finite Series Sum ??

[monir]

Hello;

1) I need to calculate M43:: sum[m=1 to m=9] G(m)*sin(m*x) for a value of
"x" tabulated in column L.
The 9 values of "m" are tabulated in $D$21:$D$29
The 9 values of G(m) are tabulated in $C$21:$C$29
The first x value is in cell L43

Can someone please help in deriving the array formula to be entered in M43 ??
For other values of x in L44, L45, ... one would simply copy M43 and paste
in M44, M45, ...

2) The following formula "obviously" doesn't work:
M43::{=SUMPRODUCT($C$21:$C$29,SIN(PRODUCT($D$21:$D$29,L43)))}

3) If it's not too much trouble, how about:
N43:: -sum[m=1 to m=9] G(m)*cos(m*x)/m for each value of tabulated x

Your help would be greatly appreciated.

Regards

 

[Shane Devenshire]

Hi,

I have no idea what this is supposed to do but 1. You don't need array
entry, 2. PRODUCT serves no purpose, so try:

=SUMPRODUCT($C$21:$C$29,SIN($D$21:$D$29*L43))

I get an answer, but of course I made up some of the numbers
Also, before you go too far on this one there is a SERIESSUM function in
Excel which you might want to look at. The Analysis ToolPak must be attached
to use it - Tools, Add-ins, and check it.

 

[monir]

Hi Shane;

Perfect !!

1) Your formula:
=SUMPRODUCT($C$21:$C$29,SIN($D$21:$D$29*L43))

2) Here're an example:
L43::1.8234766
C21::-3.29564E-02
C22::4.57676E-03
C23::-2.65454E-04
C24::1.01688E-04
C25::5.23952E-05
C26::1.12230E-05
C27::-5.97725E-07
C28::8.62970E-06
C29::3.98340E-06

D21::1
D22::2
D23::3
D24::4
D25::5
D26::6
D27::7
D28::8
D29::9

3) Your formula returns:: -0.0338 369 70
and the correct answer is:: -0.0338 369 70

Thank you kindly for your help.

Hi,

I have no idea what this is supposed to do but 1. You don't need array
entry, 2. PRODUCT serves no purpose, so try:

=SUMPRODUCT($C$21:$C$29,SIN($D$21:$D$29*L43))

I get an answer, but of course I made up some of the numbers
Also, before you go too far on this one there is a SERIESSUM function in
Excel which you might want to look at. The Analysis ToolPak must be attached
to use it - Tools, Add-ins, and check it.

Hello;

1) I need to calculate M43:: sum[m=1 to m=9] G(m)*sin(m*x) for a value of
"x" tabulated in column L.
The 9 values of "m" are tabulated in $D$21:$D$29
The 9 values of G(m) are tabulated in $C$21:$C$29
The first x value is in cell L43

Can someone please help in deriving the array formula to be entered in M43 ??
For other values of x in L44, L45, ... one would simply copy M43 and paste
in M44, M45, ...

2) The following formula "obviously" doesn't work:
M43::{=SUMPRODUCT($C$21:$C$29,SIN(PRODUCT($D$21:$D$29,L43)))}

3) If it's not too much trouble, how about:
N43:: -sum[m=1 to m=9] G(m)*cos(m*x)/m for each value of tabulated x

Your help would be greatly appreciated.

Regards

 

[Shane Devenshire]

Hi,

Glad to help.

Cheers,
Shane Devenshire

Hi Shane;

Perfect !!

1) Your formula:
=SUMPRODUCT($C$21:$C$29,SIN($D$21:$D$29*L43))

2) Here're an example:
L43::1.8234766
C21::-3.29564E-02
C22::4.57676E-03
C23::-2.65454E-04
C24::1.01688E-04
C25::5.23952E-05
C26::1.12230E-05
C27::-5.97725E-07
C28::8.62970E-06
C29::3.98340E-06

D21::1
D22::2
D23::3
D24::4
D25::5
D26::6
D27::7
D28::8
D29::9

3) Your formula returns:: -0.0338 369 70
and the correct answer is:: -0.0338 369 70

Thank you kindly for your help.

Hi,

I have no idea what this is supposed to do but 1. You don't need array
entry, 2. PRODUCT serves no purpose, so try:

=SUMPRODUCT($C$21:$C$29,SIN($D$21:$D$29*L43))

I get an answer, but of course I made up some of the numbers
Also, before you go too far on this one there is a SERIESSUM function in
Excel which you might want to look at. The Analysis ToolPak must be attached
to use it - Tools, Add-ins, and check it.

Hello;

1) I need to calculate M43:: sum[m=1 to m=9] G(m)*sin(m*x) for a value of
"x" tabulated in column L.
The 9 values of "m" are tabulated in $D$21:$D$29
The 9 values of G(m) are tabulated in $C$21:$C$29
The first x value is in cell L43

Can someone please help in deriving the array formula to be entered in M43 ??
For other values of x in L44, L45, ... one would simply copy M43 and paste
in M44, M45, ...

2) The following formula "obviously" doesn't work:
M43::{=SUMPRODUCT($C$21:$C$29,SIN(PRODUCT($D$21:$D$29,L43)))}

3) If it's not too much trouble, how about:
N43:: -sum[m=1 to m=9] G(m)*cos(m*x)/m for each value of tabulated x

Your help would be greatly appreciated.

Regards