00:01
So in this question, they say some of the highest tides in the world occur in the bay of fundy on the atlantic coast of canada.
00:09
At hopewell cape, the water depth at low tide is about 2 meters, and at high tide it is about 12 meters.
00:15
The natural period of oscillation is a little more than 12 hours, and on june 30, 2009, high tide occurred at 6 .45 a .m.
00:25
This helps explain the following model for the water depth d in meters as a function of time t, in hours after midnight on that day.
00:35
What we have in this question is d of t, and my d of t is equal to 7 plus 5 times the cosine of the quantity of 0 .503 times the quantity of t minus 6 .75.
00:55
I want to know how fast was the tide rising or falling at the following times.
00:59
I'm going to round my answer to two decimal places.
01:03
5 a .m.
01:04
6 .m.
01:04
6.
01:04
7.
01:04
6 a .m., 8 a .m.
01:06
And 11 a .m.
01:08
So if i want the rate of change of the tide's height, i need my derivative.
01:15
I need my d prime of t.
01:18
So what's my derivative? the derivative of 7 is 0.
01:22
The derivative of that constant is 0.
01:25
The derivative of this second term, i'm going to use the chain...