HP-50g derivatives

[Carsen]

Make sure that in RPN mode, put the variable T onto the stack by pressing the [ ' ] key first and then [ALPHA] [T] [ENTER]. This is the key to this entire problem because it puts the letter T onto the stack without turning into the S^2. Now you can press the [SIN] key and it should say SIN(T) on level 1. Then, put the variable T on the stack again with the same process, press the [ ' ] key and then press [ALPHA] [T] [ENTER]. Now all you need to do is execute DERIV or ∂ function above the [COS] key to derive the function, which gives you COS(T). Then use the EXPAN function to transform the answer COS(T) into COS(S^2).

For ALG mode, I have tried to attached a picture that has the steps I used to get my answer but I couldn't. It said that my file was too big. So I will have to explain it with words again. Notice how the EXPAN function is around the derivative so that it looks like this BEFORE pressing enter...

EXPAND(∂T(SIN(T))

That's the key to getting this to work. I have tried doing the exact same command without the EXPAND function around the derivative but it did not work. I got the answer 0. You - for some odd reason - NEED the derivative function inside the EXPAND function.

You also need to use the derivative function that is on the [COS] key when using ALG mode. It's the shifted orange function that looks like this...

∂

Are you doing that? Do you know how? I have tried to use the DERIV function inside the expand function but it does not work. You need to also use the derivative function that is shifted on the [COS] key.

Any confusion? Any more questions? Please ask! I am definitely not an expert of this machine so explaining why the derivative needs to be inside the expand function is beyond my knowledge. I had the same problem with my limit problems except it said "Error: Non algebraic in expression".So I figured out that I needed to have my limit inside the EXPAN function in order to get an answer and it worked. I have only owned this machine for about 6 months now.

Although, my guess is that ALG mode is somewhat incomplete and that's why the EXPAN function is needed. I don't really know though. Anyway, I hope this gets you the explanation you need.