The amount of water, A, in thousands of litres, available in a water tank located on a farm fluctuates in a yearly cycle and can be modelled by the function A(t) = a sin (kt) +b, where t is the elapsed time, in weeks, since the start of the year. The amount of water available in the tank on week 6 is 24 thousand litres and on week 31 is 9.2 thousand litres. (a) Find the value of k, in degrees, assuming there are 52 whole weeks in a year. (b) Set up a pair of equations to find the value of a and the value of b. Give your answers correct to the nearest integer. (c) Hence find the amount of water available in the tank in week 42. A(t) on the grid below, for one full year, indicating clearly (d) Draw the graph of the minimum and maximum points.

4. As a tornado moves, its speed increases. The function S(d) = 93 log d + 65 a) Graph this function. b) Calculate the average rate of change for the speed of the wind at the centre of a tornado from mile 10 to mile 100. c) Estimate the rate at which the speed of the wind at the centre of a tornado is changing at the moment it has travelled its 10th mile and its 100th mile. d) Use your graph to discuss how the rate at which the speed of the wind at the centre of a tornado changes as the distance that the tornado travels increases.

When drugs are administered into the bloodstream, the amount of the drug present decreases continuously at a constant rate. The amount of a certain drug, Xanaz, in the bloodstream is modeled by the function, where is the initial dosage, and t is the time (in hours) after the initial dose was given. The following chart shows the relationship between the original dose and how much is sti in the system after so much time. Xanax (3mg) amount still in system after X hours 2.5 1.5 0.5 2 10 12 14 16 18 20 22 24 Number of hours after dose was taken After how many hours will there be approximately 1/2 of the original dose in the body? 3. 2. 1. Amount still in the system in mg's