Output Formatting..PLEASE HELP!

[xr80dirtrider]

I am trying to do derivatives with my TI-89 and all of a sudden the formatting of the answers is all messed up and I'm not sure why. Say i enter the following

d/dx(2sin(x),x)

i am expecting it to output 2cos(x) but instead it outputs

2cos(5542168674699/2000000000000)

how can i fix it to output it the right way?

[tutorman]

Try to clear your defined variables. I believe you hit F5 or F6 and choose clear a-z. Then try that.

Hope it helps