00:01
The things that really matter to me for this first one, i think it's number three, and we want to cosine, make a little note to myself, is that we're starting at zero negative one, it goes down here to two negative seven, and then up here copies again at four negative one.
00:20
So what i like to do is before doing the amplitude figure out the midline, and so halfway between the minimum and the maximum divided by two.
00:31
So i believe i'm looking at negative eight divided by two is negative four, although in this problem they actually call that the vertical shift.
00:39
So let me just write b s equals negative four.
00:44
I know it's like the fourth question there, but that helps me do the amplitude then because i can see we're going from negative one to negative four, which means my amplitude is three.
00:55
The period, let me just use a different color, is going from zero to four, so the period is equal to four.
01:03
And then there's a phase shift question, which actually i would just write zero, or you might write none.
01:11
I don't know what you want to write, but that would be it.
01:14
Now what's the equation is we're going to write as y equals three, because that's the amplitude, cosine of, with a period of four, i have to actually write as two pi over four, which reduces to pi over two x, and then minus, because it's a negative, so adding the vertical shift, and that should be a good answer there.
01:40
And looks like off to the side they also have a, b, c, and d.
01:44
I'm going to guess that a is three, b is pi over two, c is that zero, that none there, and then d would be negative four.
01:54
It's just a weird question.
01:55
I don't know if i've ever seen that before.
01:57
But then there's another question.
01:59
This time they want the sine for number four, and i spent so much time looking at the other one, i didn't really look at this one yet.
02:08
So it looks like we're starting at negative ten.
02:12
I really had to squint my eyes and look at it.
02:15
Zero, negative ten, and then what is that? i gotta zoom in...