How many sides does a trapezoid have?
Tangential trapezoid Tangential trapezoid In Euclidean geometry, a tangential trapezoid, also called a circumscribed trapezoid, is a trapezoid whose four sides are all tangent to a circle within the trapezoid: the incircle or "inscribed circle". It is the special case of a tangential quadrilateral in which at least one pair of opposite sides are parallel. As for other trapezoids, the parallel sides are called the bases and the other two sides the "legs". The legs can be equal (see isosceles tangential trapezoid below), but they don't have to be. Examples of tangential trapezoids are rhombi and squares. A convex quadrilateral is tangential
Trapezoid two adjacent acute angles on its longer "base" edge, while an obtuse trapezoid has one acute and one obtuse angle on each "base". An isosceles trapezoid is a trapezoid where the sides (legs) have the same length, and the base angles have the same measure. It has reflection symmetry. This is possible for acute or right trapezoids. A parallelogram is a trapezoid with two pairs of parallel sides. A parallelogram has central 2-fold rotational symmetry (or point reflection symmetry). It is possible for obtuse or right trapezoids. A tangential trapezoid is a trapezoid that has an incircle. A Saccheri quadrilateral