Short Answer 
A quadrilateral is a polygon with four sides, vertices, and angles, totaling 360 degrees in internal angles. It is identified by properties such as vertices, sides, diagonals, and angles, and calculations related to quadrilaterals may involve determining lengths or areas using methods like the Pythagorean theorem.
Step 1: Understand the Definition of a Quadrilateral
A quadrilateral is a type of polygon that features four sides, four vertices, and four angles. It is formed by connecting four non-collinear points in a closed shape. The total of all internal angles in any quadrilateral sums up to 360 degrees.
Step 2: Identify Key Properties of Quadrilaterals
Each quadrilateral can be characterized by its properties, which include:
- Vertices: The corners of the quadrilateral where two sides meet.
- Sides: The straight lines that connect the vertices.
- Diagonals: The lines drawn between opposite vertices that help define its shape, labeled in the example as AC and BD.
- Angles: The angles formed at each vertex.
Step 3: Calculate Various Measures Related to Quadrilaterals
To perform calculations concerning a quadrilateral, you may need to determine specific lengths or areas. For instance:
- Calculate the side lengths using the Pythagorean theorem when applicable.
- Find half of a total distance, such as calculating SW = 21.21/2 = 10.61.
- Derive other lengths by halving values as shown, like PN = 46/2 = 23.