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# HP 40gs, how to display variables in the variables form (not numbers)

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HP 40gs

Hi!

I recently bought a second-hand calculator HP 40gs and even reading the user manual, I'm having some problems.

I would like to store two matrices in this form:

[sin(theta); cos(theta), sin(theta); cos(theta)]

[cos(theta); sin(theta), cos(theta); cos(theta)]

and then make the multiplication, willing to have the result in the form of

[sin(theta)cos(theta);.............]

instead of having the numbers shown.

The problem is that as soon as I fill the matrices with for example sin(T), it reads the T variable (which has not been yet defined, so it's considered =0) and in the matrix shows 0, instead of sin(T) literally typed.

Is there a solution to this?

Marco

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You have to use the "CAS" button and 2D editing screen. That is the only place in the calculator that does not automatically evaluate variables (A-Z and Theta ARE predefined as 0 unless you have stored something in there). Are you doing things in teh CAS screen?

TW

Although I work for the HP calculator group as a head developer of the HP Prime, the views and opinions I post here are my own.
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Hi,

I entered the CAS mode, but I can't find the 2d editing that you mentioned. Learning about the CAS from the user manual, I understood that for example in order to multiply the following matrices

1) {{S2+1,1},{3,5}}

2) {{S2+2,1},{7,5}}

I have to write, in the HOME folder

XQ({{S2+1,1},{3,5}})STO>L1
XQ({{S2+3,1},{7,5}})STO>L2
AXL(L1)*AXL(L2)

Anyway, it doesn't solve the multiplication, it shows

{{7+(S2+1)*(S2+3),......},{....,....}}

How can I make it so that it shows directly the solved products?

Thanks.

Marco

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