subtend

verb

• 1 Geometry (of a line, arc, or figure) form (an angle) at a particular point when straight lines from its extremities are joined at that point: the angle subtended by a string of length r at the centre of the sphere
• (of an angle or chord) have bounding lines or points that meet or coincide with those of (a line or arc).

• 2 Botany (of a bract) extend under (a flower) so as to support or enfold it: the main beauty is provided by the bracts which subtend the flowers