00:01
So in number one, i have a triangle and that's abc.
00:08
Side a is 12 centimeters, b is 10, oh sorry, meters, and c is 14.
00:18
And i want to find the value of angle a.
00:23
So i'm going to use law of cosines, and i'm just going to rewrite that.
00:31
So cosine of a is going to be a squared minus b squared minus c squared divided by negative 2bc.
00:40
That's 12 squared minus 10 squared minus 14 squared over negative 2 times 10 times 14.
00:52
So let's calculate.
00:54
My denominator is just negative 280.
00:59
My numerator, 12 squared minus 10 squared minus 14 squared, that's negative 152, and that's cosine a.
01:10
I'm just going to bring this over here to save some space.
01:14
So divide negative 152 by negative 280, that's 0 .5429.
01:22
Use the inverse cosine and you'll get your measure.
01:28
So second cosine 0 .5429, that's going to give me, is it telling me what to round to? no...