They are going to replace sheet metal at the roof. Wiklunds Tak-Fasad-Vent need to calculate how much material they will need. 
At a drawing they could see the measures from above (6 meter x 4,5 meter, picture 1). In the reality the roof is leaning with an angel of 30 degrees (picture 2). 

Picture 1	Picture 2
6 m	30°
4,5 m	2,25 m

How many sheet metals do they have to order to cover the roof, one sheet metal is 1 m x 6 m?