# Thread: No one knows how to do this question.?

1. ## No one knows how to do this question.?

Q19.A student models the evening lighting-up time by the equation L = 6.125 - 2.25cos(πt/6) where the time, L hours pm, is always in GMT ( Greenwich Mean Time) and t is in months, starting in mid-December. The model assumes that all months are equally long.

a)Calculate the value of L for mid-January and for mid-May

b)Find, by solving an appropriate equation, the two months in the year when the lighting up time will be 5pm (GMT).

c)Write down an equation for L if t were to be in months starting in mid-March.

2. Originally Posted by ansonbound

Q19.A student models the evening lighting-up time by the equation L = 6.125 - 2.25cos(πt/6) where the time, L hours pm, is always in GMT ( Greenwich Mean Time) and t is in months, starting in mid-December. The model assumes that all months are equally long.

a)Calculate the value of L for mid-January and for mid-May.

b)Find, by solving an appropriate equation, the two months in the year when the lighting up time will be 5pm (GMT).

c)Write down an equation for L if t were to be in months starting in mid-March.
a) substitute in the appropriate values of t for mid Jan and mid May and calculate L ... mid Dec is t = 0.

b) set L = 5 and solve for t

c) apply an appropriate transformation of the function's graph so that it shifts left 3 months.