Creating a Solar Model - Excel Help

[PeteWheatstraw]

Homework Statement

The problem given is...Calculate mI+1 and lI+1 at point xI+1 using equation (5), the values of the slopes at points xI+1 and xI from equation (4), and the values of mI and lI from the previous step.

Here is a screenshot of my solar model

Homework Equations

The Attempt at a Solution

I need help with columns I and J.

For column I, I have the equation entered as =SUMPRODUCT(I2+1/2*(G3+G2)*B3-B2)

For J I have =SUMPRODUCT(J2+1/2*(H3+H2)*B3-B2)

and for some reason I'm getting negative values when as it goes down it should be getting closer to 1

Thanks in advance!

 

[haruspex]

You need parentheses around B3-B2.
(Why do you need to use sumproduct? You're not using entire arrays of numbers to calculatd a single cell, are you?)

 

[PeteWheatstraw]

You need parentheses around B3-B2.
(Why do you need to use sumproduct? You're not using entire arrays of numbers to calculatd a single cell, are you?)

Thank you so much! I knew it was something obvious that would make me look stupid ;)

To your question...I'm not really sure. I'm excel illiterate and our professor expects us to use it without ever showing us anything.

 

[haruspex]

To your question...I'm not really sure. I'm excel illiterate and our professor expects us to use it without ever showing us anything.

Try removing the SUMPRODUCT() wrapper. I don't think it's doing anything.