The height above the ground of one of the seats of a Ferris wheel, in metres, can be modelled by the function

where

is measured in seconds.

a) What is the maximum and minimum height reached by any seat?

My answer:

Sub in t = 90 and t = 270 to obtain the max and the min, 15m and 1m.

Mr F says: Correct. But easier to just say that the min and max value of sin is +1 and -1 .....
b) How long does it take for the seat on this ride to rotate back to its starting point?

How exactly am I supposed to figure this out? I know I'm supposed to isolate for

, but I can only do that if I have a value for

.

Any help would be appreciated.