00:01
So in this problem, we're told that the length of side a is equal to 10, and we know that the cosine of angle b is equal to 4 fifths.
00:08
What we're trying to do is define the length of the missing sides.
00:12
Okay, well first off, we know that side a is equal to 10.
00:14
That's the opposite angle a.
00:16
So we know that this side length right here is equal to 10.
00:20
Now, we know that the cosine of angle b is equal to 4 fifths.
00:23
Remember, that's the ratio of the adjacent side over the hypotenuse.
00:27
So the adjacent side compared to angle b would be this length, which is 4, and the hypotenuse would be 5.
00:34
Now the key thing here is we need to find the ratio, because we know that the length is equal to 10, but we have that it's equal to 4.
00:41
So we have to figure out 4 times what is equal to 10? well, to solve for x, i divide both sides by 4, and 10 divided by 4 is equal to 2 .5, which means that this triangle got multiplied by 2 .5.
00:55
So to find the length of a hypotenuse, we also have to multiply it by 2 .5.
00:59
Well, 5 times 2 .5 is equal to 12 .5...