The solid angle subtended by a circular disc with application to roadsigns
Ian S. F. Jones · International Journal of Mathematical Education in Science and Technology · 1996
The solid angle subtended by a disc at an arbitrary point is derived from the fundamental definition with the help of the computer algebra package MAPLE. The result is used to examine the apparent size of a circular roadsign when viewed from the road as a function of observation position, position and size of sign. Results are compared with rectangular and square signs of the same area and centre. It is found that rectangular signs have a larger apparent size than both square and circular signs which have very similar apparent sizes.