00:01
So given this information about a triangle, what i can do is i can kind of construct a triangle on the side with angles a, capital a, b, and c, and sidelines across from the angles, lowercase a, lower case a, lower case b, and lower case c.
00:13
So i have some information here.
00:15
I know that a, i found angle a is 42 degrees, angle b is 61 degrees.
00:21
Is there a way i could find angle c? well, i can find angle c since the sum of all the angles in a triangle adds to 180, so i could just take.
00:30
108 degrees minus the two other angles that i have here.
00:35
And this will lead me with angle c is exactly 77 degrees.
00:43
So i found angle c done with that.
00:47
Okay, what else do i have? i have angle a.
00:51
Let's see, what else can i find? i want to find angle b.
00:54
Okay, so i know this side length across from a or the angle across from side length a and the angle across from side length b.
01:02
So the question is here would i use law of signs or what i use law of cosines.
01:08
Remember law of cosines is when we have more sides than angles.
01:12
When i have more angles than sides, i'm going to use law of signs.
01:14
So i'm going to do sign of one angle.
01:17
So sign of angle a, 42 degrees over side length a, which is going to be 12, equals sign of angle b, which is 61 degrees over side length b...