00:01
In this video, we're going to be finding the measure of angle a in degrees.
00:08
And what we need is an exact answer as required in the instructions.
00:17
Angle a can be obtained using the cosine rule as follows.
00:26
The cosine rule states that a squared equals b squared plus c squared, minus 2bc, cos a.
00:41
In this diagram, the length opposite angle a is taken to be the lower case a and the length opposite c is the lower case c.
00:53
And finally, b is a square root of 2.
00:58
So what we need to do is to substitute a squared with the square root of 5 squared plus b squared, square root of 2 squared plus c squared 3 squared minus 2 times square of 2 times square of 10 cross a all right next we can simplify since going to simplify to 5 equals 2 plus 9 minus okay something is wrong here so i'll just go back a bit it's not supposed to be 2 times square of 2.
01:45
Sorry, it's 2 times square of 2 times 3, not not square root of 10.
01:53
Let's just change that.
01:54
That's the length c is 3.
01:57
So that's 3.
01:59
Okay, so it's going to be 2 plus 9 minus 6 square root of 2, cos a...