Grades 11-12 Video Solutions 2012-2012_11-12

Video Transcription

What is the size of the angle alpha in the regular five-pointed star?  So let's take a look at this. We know that this pentagon right here is a regular pentagon. So these two angles are equal, and they're both equal to 108 degrees.  Well, this line in total has 180 degrees, so that means this angle right here, as well as this angle, they both have to be 72 degrees.  And then since this triangle has 180 degrees in total, and we already have 72 and 72, that means that this angle has to be the rest, which is 36 degrees.

Video Summary

What is the size of the angle alpha in the regular five-pointed star? So let's take a look at this. We know that this pentagon right here is a regular pentagon. So these two angles are equal, and they're both equal to 108 degrees. Well, this line in total has 180 degrees, so that means this angle right here, as well as this angle, they both have to be 72 degrees. And then since this triangle has 180 degrees in total, and we already have 72 and 72, that means that this angle has to be the rest, which is 36 degrees.

Keywords

regular pentagon

five-pointed star

angle calculation

geometry

angle alpha