TRIANGLES

__Perimeter of a Triangle__

If are the lengths of the sides of any triangle. Then:

- Perimeter of a triangle units
- Area of the triangle

where .This is also known as

__Area of a Triangle__

Refer to the adjoining figure. If b is the base and h is the height, then

Note: If you could take any side as the base, then the corresponding height is the

would be the length of the perpendicular to this side from the opposite vertex.

__Area of Right Angled Triangle__

Let the , with . Please refer to the adjoining figure.

__Area of an Equilateral triangle__

In an equilateral triangle, all three sides are equal.

Let us say the side unit.

- Height of an equilateral triangle = units
- Area of an equilateral triangle with side units

__RECTANGLE & SQUARE__

__Perimeter and Area of Rectangle__

If the sides of a rectangle are units and units (refer to adjoining figure), then

- Perimeter of rectangle units
- Area of rectangle sq. units
- Diagonal of a rectangle units

__Perimeter and Area of a Square__

If the sides of a square is units, then

- Perimeter units
- Area units
- Diagonal of a square units

__PARALLELOGRAM, RHOMBUS AND TRAPEZIUM__

__Area of a Parallelogram__

Let ABCD be a Parallelogram with base b and height h units. Let AC be the diagonal. Refer to the adjoining figure.

sq. units.

__Area of a Rhombus__

Please refer to the adjoin diagram. Let are the diagonals of the Rhombus. We know that the diagonals intersect at right angles and bisect each other.

sq. units

__Area of a Trapezium__

Please refer to the adjoining figure.

__CIRCLE__

__Circumference and Area of a Circle__

Let the circle be of radius r

Circumference of the circle

Area of the circle

__Area of a Ring (shaded area)__

Refer to the adjoining figure. The radius of the larger circle is R and that of the smaller circle is r. Area of the ring is the shaded area.