| 单词 | cone |
| 释义 | cone 1(in optics) A type of light-sensitive receptor cell, found in the retinas of all diurnal vertebrates. Cones are specialized to transmit information about colour and they function best in bright light. They are not evenly distributed on the retina, being concentrated in the fovea and absent on the margin of the retina. Compare rod. 2(in mathematics) A solid figure generated by a line (the generator ) joining a point on the perimeter of a closed plane curve (the directrix ) to a point (the vertex ) outside this plane, as the line moves round the directrix. If the directrix is a circle, the figure is a circular cone standing on a circular base. If the line joining the vertex to the centre of the base (the axis ) is perpendicular to the base the figure is a right circular cone , which has a volume πr2h/3, where r is the radius of the base and h is the height of the vertex above the base. If the axis of the cone is not perpendicular to the base, the figure is an oblique cone . In general, the volume of any cone is one third of its base area multiplied by the perpendicular distance of the vertex from the base. |
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