When i plug in:
Sqrt[82582.7813 - 69915.2788*Cos[98.005]]
on my ti-84 plus calculator, it says the answer is 303.8406641, but when i do the exact same problem on my computer (using Wolfram Mathematica) it gives me 373.71431795825 instead.. I am sure i did not make a typo, i even re-typed the equation several times, and every time i got the same answer. And I know the computer is right because in the context i was using it, the other answer made no sense.
What is wrong with my calculator?? How do i fix it?
Simple: your calculator is set to Degree mode, while Wolfram Mathematica calculates in radians. Simply switch your calculator back into Radian mode by pressing [Mode] and choosing the appropriate setting.
I came up with the same answer your ti-84 has.