4. It’s an upright angle that measures 90 degrees.
http://www.fmm.ru/pictures/vitr77a/4667k1.jpg
https://farm3.staticflickr.com/2222/2153994
497_e60b3ea324.jpg
http://static.panoramio.com/photos/large/35656766.j
pg
5. A sharp angle that measures under 90 degrees.
http://files.abovetopsecret.com/images/member/78570e5b0ef1.jpg
http://image.architonic.com/imgTre/09_10/ishigami-
yamamoto-2.jpg
6. It is a large angle that measures over 90 degrees.
http://3.bp.blogspot.com/-
eaq0soe1LbA/Utd115abfzI/AAAAAAAAAE4/KFV0Y8mFLio/s1600/chairs.jpg
http://1.bp.blogspot.com/-
7dGLQDcwyVc/TgSyZQdXKQI/AAAAAAAACV4/xZHJcPSWe
rU/s320/IMG_2721.jpg
http://4.bp.blogspot.com/-aAuz-
czJZrk/T9ETBP3rYKI/AAAAAAAAAYc/52L9OeD67sI/s1600/IMG_0300.JPG