Reasoning in Geometry

Today we had a recap on angles, this angle is a revelation angle or a 360 angle. To find out what y and x is we have to cover the bottom left line then it would look like the picture below.

This angle is a straight angle or a 180 angle, to find out y we have to take away 90° from 180 then you get 90 so y=90.

This is the same angle as the one on top, since we already know that y is 90 so we do 180°-90° then that equals 90° so x=90°