Important quadrilateral formulas

We can determine the unknown angle measure by subtracting the sum of the three known angles from 360°. Angles in a quadrilateral (that is a 4 sided shape) add up to 360 degrees. So if you are asked to work out a missing angle in a quadrilateral then add up the 3 angles that are given and subtract this answer from 360.

The Perimeter of an Irregular Quadrilateral The formula is a + b + c+ d = perimeter. For example, suppose that a quadrilateral has sides with lengths of 1, 5, 3 and 4 inches. The perimeter equals 1 + 5 + 3 + 4 or 13 inches.

If we suppose the length of a square is L, then the length of the diagonal = L √2. Area of a square = L2. A quadrilateral whose four sides are all congruent in length is a rhombus. Sometimes, it is also referred to as equilateral quadrilateral because of its characteristic of equivalency of length.

If both pairs of opposite sides of a quadrilateral are parallel, then it’s a parallelogram (reverse of the definition). If both pairs of opposite sides of a quadrilateral are congruent, then it’s a parallelogram (converse of a property).

To prove that it is a parallelogram, remember that the definition of a parallelogram is a quadrilateral with two pairs of parallel sides. Therefore, one way to prove it is a parallelogram is to verify that the opposite sides are parallel. From algebra, remember that two lines are parallel if they have the same slope.

To prove a quadrilateral is a rhombus, here are three approaches: 1) Show that the shape is a parallelogram with equal length sides; 2) Show that the shape’s diagonals are each others’ perpendicular bisectors; or 3) Show that the shape’s diagonals bisect both pairs of opposite angles.

A parallelogram is a special type of quadrilateral that has equal and parallel opposite sides. We also see a lot of parallelogram like shapes and objects around us. Properties of parallelogram. The opposite sides of a parallelogram are parallel to each other.

DEFINITION: A parallelogram is a quadrilateral with both pairs of opposite sides parallel. THEOREM: If a quadrilateral has 2 sets of opposite sides congruent, then it is a parallelogram. THEOREM: If a quadrilateral has 2 sets of opposite angles congruent, then it is a parallelogram.

In order to be a quadrilateral, a polygon must have 4 sides, and parallelograms always have 4 sides. In order to be a parallelogram, a polygon must have 4 sides with opposite sides parallel. Quadrilaterals always have 4 sides, but do not always have opposite sides parallel.

A parallelogram is a quadrilateral in which both pairs of opposite sides are parallel . Opposite sides are congruent; Adjacent angles are supplementary; The diagonals bisect each other.

One pair of opposite sides are both parallel and congruent. So, when opposite sides are equal in a Quadrilateral it is a parallelogram. The Condition which are not Sufficient to prove that a quadrilateral is a parallelogram: II: A pair of adjacent angles are supplementary.