|
circle
circle closed plane curve consisting of all points at a given distance from some fixed point, called the center. A circle is a conic section cut by a plane perpendicular to the axis of the cone. The term circle is also used to refer to the region enclosed by the curve, more properly called a ci...
Read more
|
|
chord
chord , in geometry, straight line segment both end points of which lie on the circumference of a circle or other curve; it is a segment of a secant . A chord passing through the center of a circle is a diameter. In the same circle or in equal circles, equal chords subtend equal arcs and equal cent...
Read more
|
|
hour circle
hour circle in astronomy, a secondary axis in the equatorial coordinate system . The hour circle of a celestial body is the great circle on the celestial sphere that passes through both the body and the north celestial pole. A star's hour circle is used in determining its right ascension and ...
Read more
|
|
quadrant
quadrant 1 In analytic geometry, one of the four regions of the plane determined by two lines, the x- axis and the y- axis. Commonly these lines are drawn perpendicular to each other, and the quadrants, or regions, they determine are numbered counterclockwise, beginning with the upper right qua...
Read more
|
|
vertical circle
vertical circle in astronomy, the great circle on the celestial sphere that passes from the observer's zenith through a given celestial body. In the altazimuth coordinate system the altitude of a body is measured along its vertical circle.
...
Read more
|
|
cylinder
cylinder in mathematics, surface generated by a line moving parallel to a given fixed line and continually intersecting a given fixed curve called the directrix; each line of the family of lines forming the cylinder is called a ruling, or generator. If the directrix is a conic section (e.g., a ci...
Read more
|
|
cone
cone or conical surface, in mathematics, surface generated by a moving line (the generator) that passes through a given fixed point (the vertex) and continually intersects a given fixed curve (the directrix). The generator creates two conical surfaces—one above and one below the vertex&md...
Read more
|
|
nimbus
nimbus , in art, the luminous disk or circle or other indication of light around the head of a sacred personage. It was used in Buddhist and other Asian art and by the early Greeks and Romans to designate gods and heroes and appeared in Christian art in the 5th cent. Although usually a circle or dis...
Read more
|
|
sphere
sphere in geometry, the three-dimensional analogue of a circle . The term is applied to the spherical surface, every point of which is the same distance (the radius) from a certain fixed point (the center), and also to the volume enclosed by such a surface. The curve formed by a plane cutting a sp...
Read more
|
|
transit instrument
transit instrument or transit, telescope devised to observe stars as they cross the meridian and used for determining time. Its viewing tube swings on a rigid horizontal axis restricting its movements to the arc of the meridian. In the field of view of the eyepiece are threads of spider web or ...
Read more
|