One of the important issues in photometry and radiometry is the surface area calculation, or knowing its relative surface element for any integration or other metrology aims. In this paper, firstly, we have reviewed the oblique cross-section of a right circular cone (OCRCC), then we have derived how to choose an elementary surface area or infinitesimal small patch on the elliptical surface of OCRCC, accurately. This surface element derivation maybe looks ordinary, but it has a major importance to calculate a part of the OCRCC surface. Such geometrical element can be applied to solve physics problems included certain lighting and photometry issues. Therefore, we have produced and presented related schemes and illustrative examples, then we have solved certain of them numerically by “Mathematica”. These examples clarify the lighting or photometric applications of this new surface element and validate its correctness.

光度法和辐射度法中的重要问题之一是表面积的计算，或者知道其相对表面元素以进行任何积分或其他度量目的。在本文中，首先，我们回顾了右圆锥（OCRCC）的斜截面，然后得出了如何在OCRCC的椭圆形表面上准确选择基本表面积或无穷小的小斑块。这种表面元素推导看起来很普通，但是计算OCRCC表面的一部分非常重要。可以将这种几何元素应用于解决包括某些照明和测光问题的物理问题。因此，我们制作并提出了相关的方案和说明性示例，然后通过“ Mathematica”用数值方法解决了其中的某些问题。