Subtend

verb

1. To use an angle to delimit (mark off, enclose) part of a straight or curved line, for example an arc or the opposite side of a triangle.
2. (also mathematics) To extend or stretch opposite something; to be part of a straight or curved line that is opposite to and delimits an angle.

   "A hypotenuse subtends the right angle of a right triangle."

3. To form the central angle of a circle underneath an arc

   "The points A and B on the circumference form the arc AB, which subtends the central angle θ."