00:01
Okay, so i'm given a parallelogram like so.
00:05
It says that the sides are three and five.
00:10
So one of the sides is three, one of the sides is five, and i know that one angle is 50 degrees.
00:17
Okay.
00:18
So from what i know about a parallelogram, i know that opposite sides are equal, and opposite angles are also equal.
00:28
I also know that two corresponding angles, two angles right next to each other are supplementary, and supplementary means they add up to 108 degrees.
00:40
So i know that another angle off to the size is going to be 130, 130 is going to be over here, and 50 is also going to be over here, and all the angles are going to add up to 360.
00:50
Okay.
00:51
So my goal in all this is i want to find the length of the diagonals.
00:56
So let's call this first diagonal and say i wanted to find x.
01:02
Well, i have a triangle, right? i cut the parallelogram in half.
01:06
I'm given side angle side, right? side five, angle 50 degrees, side three.
01:14
And i want to find the side across from that angle.
01:18
So given side angle side, if i'm looking for another side, i can use law of cosines.
01:27
So to find the length of the diagonal x, i'm going to start with it...