Three planes, e, f, and g intersect so that each is perpendicular to the other two. a segment ab is positioned so that the length of its projection on the intersection of e and f is 1, on the intersection of f and g is 2, and on the intersection of e and g is 3. what is the length of ab?
a) radical 14
b) 4
c) 5
d) 6
e) radical 12

Three planes, E,F and G, intersect so that each is perpendicular to the other two. A segment AB is positioned so that the 
Length of its projection on the intersection of E and F = 1, 
Length of its projection on the intersection of F and G = 2 
Length of its projection on the intersection of E and G = 3. 
Length of AB =√{(1)²+(2)²+(3)²}=√{1+4+9}=√14 
Hence a.