I am trying to find the zeros of the sine function below when i do maple just returnes 0.

I just started with maple 16 trying to complete an into assinment.  I am in a worksheet trying to just enter simple expresions 3+4 or 3*4 ect.  Whne i enter the operator + * using the keyboard, ther operators menu or pasting from notepad about 90%  of the time the previous number i typed disapears and the worksheet will no longer accept imput

I have tried reinstalling several times with no AV active even installed in safe mode same issue..

Maple...