Q.Is equilateral Trapezium possible?
The defination of Trapezium :A quadrilateral with one pair of parallel sides.
If we have a trapezium that have equal sides,it becomes a rhombus (& contradicts it's own defination). This implies that equilateral trapezium is not possible.
A quadrilateral that is both a trapezium (in those countries that call football soccer: a trapezoid) and a rhombus is a square. Note that "one pair" i the definition of trapezium is understood as "at least one pair"
Apart from that, the term "equilateral (or: isosceles) tapezium" is used for a trapezium where (only) the non-parallel (or not necessarily parallel) pair of sides are of the same langth.