Assertion: tetrahedron's face | /r/HasProperty | f l
Facets:
Source sentences:
text: Take the general tetrahedron X {\displaystyle X} and project the faces F i , F j , F k {\displaystyle F_{i},F_{j},F_{k}} onto the plane with the face F l {\displaystyle F_{l}} .
text: Then the area of the face F l {\displaystyle F_{l}} is given by the sum of the projected areas, as follows: