differentiating with e^x function

[MadMax]

I'm having a little trouble differentiating with my ti-89. When i try to differentiate y(t)=24+(B*cos1.936t+C*sin1.936t)e^-0.5t (B and C are constants) I'm getting crazy numerical values like -.5(.606531)^t.(B-3.872*C)*cos1.936t+3.8… My question is why isn't "e^" showing up in the the differentiated value? I know that the differentiated value should be something like e^-0.5t(-1.936Bsin1.936t+1.936Ccos1.936t…

[mellamokb]

Hi MadMax,

When doing approximations on a TI-89, e gets evaluated as part of the expression, as though it were the number 1.7281828..., instead of some variable or function. If you enter in exact number values and use exact mode, it may be possible or the answer to keep e in place.

Hope this helps!

Regards,
~ mellamokb