00:01
We're going to use the diagram in the boat in the picture to help us.
00:03
So we're told that we have a boat that's sailing due east parallel to the shoreline.
00:06
So here's where our boat begins.
00:08
And again, it's heading due east.
00:10
So we're told us going 10 miles per hour.
00:13
So that's our speed.
00:14
So 10 miles per hour.
00:16
So at a given time, the bearing to the lighthouse is south 70 degrees east, as they moated in the diagram.
00:22
And 15 minutes later, the bearing is south 63 degrees east.
00:27
The lighthouse is located at the shoreline, which is right here.
00:29
So we want to know the distance from the boat to the shoreline.
00:33
That's our distance deep.
00:35
Okay.
00:36
Well, first off, our boat's going 10 miles for an hour, and 15 minutes later, we know that the new bearing.
00:44
So the first thing we need to do is to figure out the distance.
00:48
Well, because it's going 10 miles an hour and it's going 15 minutes, that's only a quarter of an hour.
00:55
So to figure out the distance will take 10 and multiply it by 1 .4.
01:00
Well, that's equal to 2 .5.
01:02
So we know the distance between the two boats is 2 .5 miles.
01:08
So right now we're going to need to find a couple other pieces of information.
01:12
Well, keep in mind, this angle right here is 70 degrees, and we know that this angle has to be 90.
01:18
So the angle inside our triangle is 20 degrees.
01:22
Also note that our boat is traveling due east.
01:25
And remember, when we had in our line here to figure out our second bearing, that means this angle right here is 90 degrees...