Thread: trig with hours of daylight, days after equinox

At a certain latitude in the northern hemisphere, the number d of hours of daylight in each day of the year is taken to be d=A+Bsinkt°, where A, B, k are positive constants and t is the time in days after the spring equinox.
Assuming that the number of hours of daylight follows an annual cycle of 365 days, find the value of k, giving your answer correct to 3 decimal places.

Ok I'm not really sure where to start here, any hints would be appreciated.
Am I supposed to use -1<sinkt°<1 ? how to i fit in the 365 day with t?

The annual cycle is 365 days, so this is your period.

You should know that the period . Solve for .