This operation is performed by function cellToLatLng. See the comments in the function source code for more detail.
1. The function _h3ToFaceIjk then converts the H3 index to the appropriate icosahedron face number and normalized ijk coordinate's on that face's coordinate system as follows:
1. The face-centered ijk coordinates are then converted into corresponding Hex2d coordinates using the function _ijkToHex2d.
2. The function _hex2dToGeo takes the Hex2d coordinates and scales them into face-centered gnomonic coordinates, and then performs an inverse gnomonic projection to get the latitude/longitude coordinates.