Number series refers to numbers arranged in succession one after the other. Trigonometry is a branch of mathematics involving the study of relationships between lengths and angles of triangles, emerging from the Hellenistic world during the 3rd century BC.

6. Number Series
 It is the number arranged or
coming one after the other in
succession

8. Trigonometry
 A branch of mathematics that
involves the study of the
relationship involving the lengths
and angles of the triangles
 Emerged from the Hellenistic world
during the 3rd
century B.C.