Identity parallel lines

Define parallel lines.

Equivalent capacitance of following arrangement of identical parallel plates is

If a set of in parallel lines intersect another set of parallel lines (not parallel to the lines in 1^("st") set) then find the number of parallelograms formed.

A : IF 5 parallel lines intersect 4 parallel lines are intersecting another set of n parallel lines is ""^(m)C_(2) xx""^(n) C_(2) .

In fig. if lines l and m are parallel lines then x=

Transversal to two parallel lines:

Intersecting and parallel lines

Two lines are respectively perpendicular to two parallel lines. Show that they are parallel to each other.