The height of a buoy above the seabed, h h\,h metres, fluctuates with the waves according to the formula: h=15−5sin(60t)h = 15 - 5\sin(60t)h=15−5sin(60t), where t t\,t is the time in hours after 6:00 AM.
a.[4]
On the axes below, draw the graph of h h\,h against t t\,t for 0≤t≤60 \leq t \leq 60≤t≤6
b.[2]
Find the two values of ttt, where 0≤t≤120 \leq t \leq 120≤t≤12, when the height of the buoy is least.