39367
In this parameterisation , the ratio of " t " to " r " can be interpreted geometrically as the stereographic projection of the line passing through the centre parallel to the " x " - axis ( see Tangent half-angle substitution ) .
 Tangent
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Tangent