My casio calculator cfx is coming up with 'syn

Hello,
I believe you are not pressing the keys in the right order.
If you know how to set angle unit, skip this part and go to Exemples

If you want to calculate the sine , cosine or tangent of an angle given in degrees, the calculator must have the angle unit set to degrees. To do so :Turn calculator ON, scroll to [RUN] icon and press [EXE] then [SHIFT][SETUP]. On the fifth line angle must be set Degrees. If it is not in degrees, press the key correspondig to menu deg (F1)
(If you have to use the Radian as unit of angle, that is where you set it.)
So your angle is in degrees.
Exemples
To calculate the sine of 15 degrees press [SIN] 15 [EXE].
If expression inside the sine is complicated or contains diverse operations use parentheses as in the exemple
[SIN] [(] 90/2 -180/3 [)] [EXE].
You proceed the same way for cosine, or tangent.

Hope it helps.