Cordially welcomely!

On these sides you learn everything over the trapezoid (in North America) or trapezium (in Britain and elsewhere). Go through all sides point by point and try everything to understand. If you should see through somewhat not directly with the first time, you can go through the exercise again and again.

If it is nevertheless not understandable, you can post your problem in the forum. Perhaps someone can help you from your class. 

Much fun when learning
Georg Ratz

PS.: If you want to help me translating my elearning courses, please contact me: lessons2english@elsy.at.