Help Centripetal Force problem

[user2867]

Here's the problem. I don't understand how to get the velocity?

If you cannot read the attachment it reads:
An amusement park ride consists of a rotating
circular platform 8.26 m in diameter from
which 10 kg seats are suspended at the end
of 3.9 m massless chains. When the system
rotates, the chains make an angle of 17.9 with
the vertical.
The acceleration of gravity is 9.8 m/s2 .


I tried finding v_x then doing v_x*tanθ, but the computer said I was wrong...ANY HELP WOULD BE AMAZING!

 

[Simon Bridge]

You need to do a free-body diagram for the seat.