subtend

subtend
[sʌbˈtɛnd]
verb
[with obj.]

(of a line, arc, or figure) form (an angle) at a particular point when straight lines from its extremities are joined at that point
（线，弧，图形）对向
■(of an angle or chord) have bounding lines or points that meet or coincide with those of (a line or arc)
（角或弦）被一条直线（或弧）所截或所限
(Botany)(of a bract) extend under (a flower) so as to support or enfold it
(植)衬托

语源

late 16th cent. (in sense 1): from Latin subtendere, from sub- 'under' + tendere 'stretch'. Sense 2 dates from the late 19th cent