Skip to main content
Contribution to Book
HCR's Inverse Cosine Formula
Analysis of a tetrahedron (2014)
  • Harish Chandra Rajpoot, HCR
HCR’s Inverse Cosine Formula derived by Mr H.C. Rajpoot is a trigonometric relation of four variables/angles. It is applicable for any three straight lines or planes, either co-planar or non-coplanar, intersecting each other at a single point in the space. It directly co-relates the internal angles (i.e. angles between the consecutive lateral faces) & the face angles (i.e. angles between the consecutive lateral edges) of any tetrahedron. This formula is very useful to find out all the unknown internal angles if all the face angles of any tetrahedron are known & vice versa.
Publication Date
Winter December 6, 2014
Publisher Statement
Citation Information
Harish Chandra Rajpoot. "HCR's Inverse Cosine Formula" Analysis of a tetrahedron (2014)
Available at: