Trigonometric functions as fractions on TI-84 Plus. I know that on the TI-84, you can use mode to change settings to fraction mode. However, when I used trigonometric functions to convert them into fractions, they gave me decimals still. Is there another step you have to take in order to receive fractional answers for trigonometric functions?
E.g. In radians, cos(pi/3), which equals (sqrt(3))/2, but the calculator gives .866025...

As the other answer says, you simply can't express all values of trigonometric functions as fractions. 
I am guessing that on your TI-84, if you set the calculator to give you the fractions, then $\sin(30^\circ) = \sin(\pi /6)$ will give you $\frac{1}{2}$ (that is how it works on my TI-84). But you also know that, for example, $\sin(45^\circ) = \sin(\pi / 4)$ is equal to $\frac{\sqrt{2}}{2}$. This is not a rational number and can't be written as a ratio of two integers. 
You calculator can only find these exact fractions when the answer is a rational number.
