T = 10Sin ( (2Pi/365)*X ) + 25, is the daily average temperature in a village whereXis the day of the year.

I have constructed a table of values for 0 <X< 365 and created a graph, however when it comes to differentiating the following I am a bit lost. If someone could talk me through it that would be great:

i) The rate of change of the temperature is given bydT/dX. FinddT/dXand the rate of change of the temperature whenX= 150 .