Help with general trig equation
I don't know what this problem would be classified as, but i need help with it!
The formula F(x)=75+15sin[2π/365(x-101)] represents the fahrenheit temperature in Gainesville as a function of the day of the year. Let x represent the day of the year (in a non leap year), so x=1 represents Jan. 1 (etc.) Use this formula to determine the day(s) of the year (give the dates) when the average daily temperature will be closest to 85ºF
I graphed it in a graphing calculator and determined that the days were day 143 and day 240 (April 23rd and July 28) and plugged them into the equation and they equaled about 85, but i do not know how to work the problem out using trig functions.
Any help would be appreciated. Thank you!