**7.1- Introduction**

Use conventional terms and notation: points, lines, vertices, edges, planes, parallel lines, perpendicular lines, right angles, polygons, regular polygons and polygons with reflection and/or rotation symmetries ; use the standard conventions for labelling and referring to the sides and angles of triangles ; draw diagrams from written description

A polygon is any shape with straight sides. A** regular polygon** is where all of the interior angles are the same.

**Parallelogram:** opposite sides are parallel, opposite angles are equal, the diagonals bisect one another (this means the diagonals cross at their midpoints).

**Rhombus:** (a parallelogram with all four sides of equal length), diagonals bisect one another at right angles.

**Trapezium:** One pair of opposite sides are parallel.

**Square:** All sides are equal, all angles are 90 degrees, diagonals bisect one another at 90 degrees.

**Rectangle:** All angles are 90 degrees, diagonals bisect one another.

**7.2- Measuring lengths and angles**

A Perimeter is a one dimensional measurement. It is a length measured usually in metric units such as cm, m, km.

**Perimeter of a Circle**

The perimeter of a circle is known as the circumference. To calculate the circumference of a circle you can use one of two formulae, either: C = 2πr or C = πd. In these formulae r is the radius and d is the diameter.

**The perimeter of a rectangle**

To calculate the perimeter of a rectangle, just add all the sides together.

**7.3- Area of a 2D shape**

Area is a two Dimensional Measurement. In most countries it is measured using metric measurements such as mm^{2}, cm^{2},m^{2}, km^{2}.

Area of triangle, A=\(\frac{1}{2}\) b× h

Area of rectangle, A=b × h

Area of parallelogram, A= b×h

Area of trapezium, A=\(\frac{1}{2}\)(a+b)× h

Area of circle, A=πr^{2}

**7.4- Transformations 1**

A** translation **occurs when a shape is moved from one place to another. It is equivalent of picking up the shape and putting it down somewhere else. Vectors are used to describe translations.

A **reflection** is like placing a mirror on the page. When describing a reflection, you need to state the line which the shape has been reflected in. The distance of each point of a shape from the line of reflection will be the same as the distance of the reflected point from the line.

When describing a **rotation**, the centre and angle of rotation are given.

**7.5- Transformations 2**

**Enlargements** have a centre of enlargement and a scale factor.

If a shape has a line of symmetry, the line of symmetry will divide the shape into two equal parts, one half of which can be folded along the line of symmetry to fit exactly onto the other. Note, a rectangle has two (not four) lines of symmetry and a circle has an infinite number.

**7.6- Summary and Review**

**7.7- Assessment 7**

Question 1 : What is the area of a rhombus of length of diagonals a_{1 }and a_{2} ?