00:01
Okay, to solve this problem, you're given a diagram of two plain mirrors that meet at 70 degrees, and the ray comes out horizontally, and they want to know what angle does the ray go into this first mirror, so that it comes out of the second mirror horizontally.
00:17
Since this line right here is parallel to this line, these two angles are congruent.
00:23
So that tells us that this is a 70 degree angle up here.
00:27
We can use that information and consider the north.
00:31
Normal line to figure out more information about these angles.
00:35
The normal line is at 90 degrees, so 90 minus 70 would be 20 degrees here.
00:42
And that is going to be the same angle between this ray and the normal, which tells us that we have a 70 degree angle here...