Chapter 13, Problem 13.6P

The “crossed-strings” method of Hottel [13] provides a simple means to calculate view factors between surfaces that are of infinite extent in one direction. For two such surfaces (a) with unobstructed views of one another, the view factor is of the form
$F_{12}=\frac{1}{2w_1}\left[\left(ac+bd\right)-\left(ad+bc\right)\right]$

1. 

Use this method to evaluate the view factors F₁₂for sketches (b) through (e). Compare your results with those from using the appropriate graphs, analytical expressions, and view factor relations.