Question

Horizontal plane A and vertical plane B intersect at a line. Line n is vertical on plane B and forms a right angle with horizontal line m on plane A. Line l is diagonal on plane A.
Are the lines in the diagram perpendicular, parallel, skew, or none of these?

l and m:

l and n:

m and n:

Answer 1

l and m: none of these — both lie in horizontal plane A (so they meet) but l is a diagonal, not perpendicular to m.

l and n: skew — l lies in plane A while n is vertical in plane B; they are not parallel and (in the given picture) do not meet.

m and n: perpendicular — n is given to form a right angle with horizontal line m.