The daily average temperature in Santiago, Chile, varies over time in a periodic way that can be modeled approximately by a trigonometric function.
Assume the length of the year (which is the period of change) is exactly 365days long. The hottest day of the year, on average, is January 777, when the average temperature is about 29 degrees C.

The average temperature at the coolest day of the year is about 14 degrees C.

Find the formula of the trigonometric function that models the daily average temperature T in Santiago t days into the year. (t = 1 on January 1) Define the function using radians.

What is the average temperature in Santiago on January 31? Round your answer, if necessary, to two decimal places.