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.

 

[Nickie]

I would suggest checking your equations and data inputs carefully to ensure they are accurate. It may also be helpful to double check your calculations and consider using a different approach or formula if necessary. Additionally, I would recommend seeking assistance from a tutor or colleague who is familiar with Excel and solar models to help troubleshoot any issues you may be encountering. It is important to thoroughly understand the calculations and results in order to accurately interpret and analyze the data from your solar model.