text: The size of some of these mathematical entities is the subject of Thales's theorem.
full_question: The size of some of these mathematical entities is the subject of Thales's theorem. Euclid's fourth postulate assumed the equality of some of these entities. The trisection of these entities was shown to be impossible using straightedge and compass in 1837. A pair of intersecting planes create a "dihedral" one of these entities, while a pair of intersecting lines form two pairs of "vertical" ones. Two units which measure these entities have a conversion factor of pi over 180. For ten points, name these mathematical entities which may be measured with a protractor.
first_sentence: The size of some of these mathematical entities is the subject of Thales's theorem.