00:02
We were given this function here that describes the hours of daylight in philadelphia on the tth day of the year.
00:13
So this is the days.
00:16
So we have 12 plus 2 .8 sign of 2 pi over 365 times the quantity t minus 80.
00:24
So they want us to, let's see here, compare how much the hours of daylight is increasing in philadelphia on march 21st and may.
00:35
21st.
00:36
So we need to take a derivative.
00:37
So i use the dot for time derivative.
00:40
So we have the time derivative.
00:41
And this is really just again, this goes to zero.
00:46
And then using a chain rule here, we get two.
00:50
The rid of the sign is the cosine.
00:52
So we just get the cosine of this.
00:55
But then the chain rule of the art.
00:57
We need to take the derivative of the argument with respect to t.
01:01
So we get this times two pi over 360 and that winds up.
01:05
Being 0 .0482.
01:09
Now, march 21st is 80 days into the year...