Quadrilaterals
A quadrilateral is a polygon which has four sides.
Comparisons between different quadrilaterals based on the lengths of the sides and angles
| Quadrilateral Type | Property |
| Rhombus | It has 4 sides of equal length. |
| Square | It is a rhombus with 4 right angles. |
| Parallelogram | It has two pairs of parallel sides. |
| Rectangle | It is a parallelogram of 4 right angles. |
| Trapezium | It has one pair of parallel sides. |
Rhombus
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All the four sides are equal.
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Opposite sides are parallel.
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Opposite angles are equal.
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Diagonals intersect each other at the centre and at 90°.
Trapezium
- A trapezium is a quadrilateral where only two sides are parallel to each other.
- No sides, angles and diagonals are congruent.
Parallelogram
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It has two pairs of parallel opposite sides.
- Square and rectangle are also parallelograms.
Rectangle
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It has two pairs of equal opposite sides.
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Opposite sides are parallel.
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All the angles are the right angle.
Square
- A square is a quadrilateral which has all sides equal and all angles are right angles.
- The diagonals are equal and perpendicular to each other.
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All the four sides are equal.
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Opposite sides are parallel.
- All the angles are the right angle.
Three Dimensional Shapes
- Three-dimensional shapes are those shapes that can be projected on paper but not drawn on paper.
Faces, edges and vertices
- Each side of a three dimensional solid is called the face.
- Two faces meet at a line segment called an edge.
- Three edges meet at a point called a vertex.
All the flat surfaces of the solid shape are called the Faces of that figure.
The line segment where the two faces meet with each other is called Edge.
The point where the two edges meet with each other is called Vertex.
Some 3-D Shapes that we see in our daily life are shown in the picture given below.
No. of Faces, Edges and Vertices in some common 3- D shapes
Special 3D shapes
- Solids such as the prism and pyramid are considered as special 3D shapes since their structure is very unique.
- A prism with a triangular base is called a triangular prism.
- A pyramid with a rectangular base is called a rectangular pyramid
Angles
The amount of rotation about the point of intersection of two planes (or lines) is called angle.
Right, straight and complete angles
- Right angle is equal to 900.
- Straight angle is equal to 1800.
- Complete angle is one complete revolution or equal to 3600.
Acute, obtuse and reflex angles
- Acute angle is lesser than 900.
- Obtuse angle is greater than 900.
- Reflex angle is greater than 900.
Tools of construction
- Ruler and divider are used to measure lengths of line segments.
- A protractor is used to measure angles.
- Angles are measured in degrees.
- Angles are measured by using a protractor.
