Diagonals
In geometry, a diagonal is a line segment that connects two non-adjacent vertices of a polygon. The term "diagonal" is commonly used to refer to the line segment that connects the opposite corners of a polygon, such as a square or a rectangle.
The number of diagonals in a polygon can be calculated using the formula:
n(n-3)/2
Where n represents the number of sides of the polygon.
For example, a square has 4 sides, so the number of diagonals can be calculated as:
4(4-3)/2 = 2
So, a square has 2 diagonals.
Diagonals are important in geometry as they create new line segments within a polygon and can help in determining the area, perimeter, and other properties of the shape.
.◂Math Worksheets and Study Guides Third Grade. Solids and Faces
Study Guide
Solids and Faces 
Worksheet/Answer key
Solids and Faces Worksheet/Answer key
Solids and Faces Worksheet/Answer key
Solids and Faces Worksheet/Answer key
3D Solids Worksheet/Answer key
3D Space
Worksheet/Answer keyWorksheet/Answer keyWorksheet/Answer keyWorksheet/Answer keyWorksheet/Answer keyThe resources above cover the following skills:
Geometry (NCTM)
Analyze characteristics and properties of two- and three-dimensional geometric shapes and develop mathematical arguments about geometric relationships.
Identify, compare, and analyze attributes of two- and three-dimensional shapes and develop vocabulary to describe the attributes.
Classify two- and three-dimensional shapes according to their properties and develop definitions of classes of shapes such as triangles and pyramids.
Use visualization, spatial reasoning, and geometric modeling to solve problems.
Recognize geometric ideas and relationships and apply them to other disciplines and to problems that arise in the classroom or in everyday life.