Upper surface of a finite rectangle tilted relative to an infinite plane
The function F3D_27 returns the view factor between the upper surface of a finite rectangle tilted relative to an infinite plane.
Input:
tau = tilt angle of rectangle [deg] or [rad]
Example:
tau=90 [deg]
F=F3D_27(tau)
{Solution: F=0.5}
Reference: www.me.utexas.edu/~howell/sectionc/C-9.html