[填空题]
The average gasoline pricq wmdjpj6 ,6hrys*c/(z,gp *k k6r)uxe, P, in cents per gallon, in USA 2019 can be mkomra9.g(m (h odelled by the m((rh .gkao9m function
P(t)=acos($15^{\circ}\times$t+$90^{\circ}$)+b,0≤t≤365,
where t is the elapsed time, in days, since New Year's Eve 2018.
Part of the graph of y=P(t) is shown below.
1.Write down the value of b.
The average price of gasoline on the 14th of January, 2019 was 328 cents per gallon.
2.Show that the value of a is equal to 56. a =
3.Hence calculate:
(1)the average gasoline price on the 1414th of February, 2019; P = cents per gallon
(2)the minimum and maximum average prices of gasoline in USA 2019. $P_{min}$ = cents per gallon $P_{max}$ = cents per gallon
The cycle of average gasoline prices repeats every T days.
4.Determine the value of T. T =
