The distance of the lucid points was the tangent of the magnified angles subtended by the stars to a radius of io ft.
By geometrical consideration it can be shown that the angle subtended by p, as seen from F, must be inversely as the square of its distance r.
The potential at any point due to a magnetic shell is the product of its strength into the solid angle w subtended by its edge at the given point, or V = Fu.
The plants grow from a bulb or short rhizome; the inflorescence is an apparent umbel formed of several shortened monochasial cymes and subtended by a pair of large bracts.
We conclude that a double line cannot be fairly resolved unless its components subtend an angle exceeding that subtended by the wave-length of light at a distance equal to the horizontal aperture.