00:01
All right, guys, so in this problem, i might be reading it wrong.
00:04
It's kind of hard to understand the whole average velocity, the position.
00:09
But so if our position function, s of t, is equal to 2t, sine of 5t, well, if we want to find the velocity function, all we have to do is take the derivative of that.
00:27
So the derivative of this, so we take the derivative of the first of the 2t, so that's 2 times the sign of 5t, plus now we leave 2t alone.
00:40
We take the derivative of 5t, which is the cosine of 5t times the derivative of what we're taking the cosine of, which is 5.
00:52
So i think that's how we're supposed to type it.
00:54
So our velocity function should be 2 times the sign of 5t plus 10 t times the cosine of 5t.
01:13
And that's our velocity function with respect to time.
01:17
All right.
01:17
So now if we want the acceleration function, we just have to take the derivative of our velocity function.
01:24
Well, the derivative of 2 sign of 5t is not negative, is just 2, okay, 2 cosine of 5t times the 5.
01:41
So that's going to be 10 cosine of 5t plus now i got to do the product rule with this.
01:51
So that's going to be 10 times the cosine of 5t plus 10t times.
02:02
Now i'm taking the derivative of cosine, which is negative sign of 5t times 5 because i've got to take the derivative of what's the chain rule with the sign.
02:15
All right.
02:16
So all of this 10 cosine, so this 10 cosine of 5t was this part here.
02:24
Now, adding, i have another 10 cosine of 5t plus, so i have a negative and a 5 and a 10, so it's actually really going to be a negative.
02:47
So it'll be minus 50t times the sign of 5t...