Need help on how to set this up and the answer, so I can study it to understand it.

A shaft whose diameter is 10 cm rotates with an angular speed of 1.00 rad / second. Calculate the angular displacement IN RADIANS, if the shaft rotates for 3.75 seconds??

PLEASE HELP STUCK ON THIS>

I know you convert the diam which comes to 0.05 m for RADIUS

But don't know which formula to use tho??

THANKS for your help

Joanne