ICSE Board: Suggested Books ICSE Board: Foundation Mathematics Class 8: Reference Books Class 8: NTSE Preparation --------------------------------------------------------------
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.
Let the triangle be ABC, with B = 90. 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.
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.
Area of a Trapezium
Please refer to the adjoining figure.
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.