Take the 50mm f/1.8 II as an example.
EF 50mm f/1.8 II S$160 MM 46° 5-6 f/1.8 1.5/0.45 41 4.6/130 ES-62# 52 E-52 LP1014
Does it mean, the lights travelling in the lens form a triangle with one
side of 35mm, height of 50mm, the other two sides are equal, and the
angle opposite to this side is 46°? However,
50mm * tan(23°) * 2 <> 35mm.