foci

How to use foci in a sentence

• In an orbit made elliptical by the planetary attraction the sun necessarily occupies one of the foci of the ellipse.

  Outlines of the Earth's History | Nathaniel Southgate Shaler

• That an ellipse may be given any required proportion of width to length by locating the foci at the requisite distance apart.

  Mechanical Drawing Self-Taught | Joshua Rose

• That the proportion of length to width in an ellipse is determined by the distance apart of the foci.

  Mechanical Drawing Self-Taught | Joshua Rose

• The curve thus traced will be an ellipse having the pins at the two points which are called its foci.

  A Text-Book of Astronomy | George C. Comstock

• These are at points on the principal axis that are twice as far from O, the center of the lens, as are the principal foci.

  Physics | Willis Eugene Tower