Quadrilaterals have four sides,four angles and the interior angles of each sides added together make up 360 degrees
2a.Quadrilaterals have four sides,four angles and the interior angles of each sides added together make up 360 degrees.A square and a parallelogram both have four sides and angles and these angles make up 360 degrees when added together.Thus a square and parallelogram are quadrilaterals.
2b.Yes.Angles of the opposite sides added together should make 180 degrees which shows they are parallel and never cuts each other.
2c.A trapezoid has only one sides of parallel lines because it has only 2 pairs of opposite angles makes 180 degrees when added together while figures with 4 pairs of opposite angles which makes up 180 degrees when added together has 2 pairs of parallel lines.
Thus All of the above are correct.
3.Only a trapezium which is a quadrilateral has only one parallel lines.
4.No.They make up a rectangle.A parallelogram is made up of a square and 2 triangles.
Let's give an example:(Image Above)
A parallelogram which has a base of 8 cm and height of 3 cm.Let's cut the parallelogram into 3 parts.A rectangle,and 2 triangles,let's combine the 2 triangles and make a square.When you combine the rectangle and the combined rectangle of the two triangles you from a new rectangle of 8 x 3cm. 8 x 3cm is 24 cm square which is not a square number.
5.Since ABCD is a parallelogram and E and F is the midpoints. Since AD = BC and AE=ED which means (AE=ED) is equals to BF =FC thus AE = ED = BF = ED. As angle EBF = AEB
So angle BED + EBF =180 degrees and EDF = EBF.Thus it is a parallelogram.