Answer:
65°
Step-by-step explanation:
Since the high is given, it is convenient to use that value with a cosine function to model the temperature. The function will be ...
T = A + Bcos(C(x-D))
where A is the average temperature, B is the difference between the high and the average, C is π/12, reflecting the 24-hour period, and D is the time at which the temperature is a maximum. "x" is hours after midnight.
We have chosen to use a 24-hour clock with x=16 at 4 pm. Then the value of T at 9 am is ...
T = 70 +20cos((π/12(9 - 16)) = 70 +20cos(7π/12) ≈ 64.824
The temperature at 9 am is about 65°.
