Dynamics derivatives

[dzl13]

Hello all,

I need to know if the ti89 can do derivatives with respect to an unrelated variable. I know that probably made no sense so here is an example:

r=varibla
@=variable "theta"
r=r(t) and @=@(t)

r=cos@

find dr/dt
ans:
dr/dt=-sin(@)@'

now dr2/dt2=
-cos(@)@'^2-sin(@)@''
anyones help would be awesome.

[bostonvaulter]

as far as I know it would only work if @ is an actual function of t. So if @ was t^2, then you you get something like -2t*sin(t^2)

But there isn't a way to make @ be a generic function of t. So you'll never get @' as part of your answer