Important Facts and Formula:
Results On Triangle
1.Sum of the angles of a triangle is 180 degrees.
2.The sum of any two sides of a triangle is greater
than third side.
3.Pythagoras Theorem:
In a right angled triangle (Hypotenuse)2 = (Base)2 +(Height)2
4.The line joining the mid point of a side of a triangle
to the opposite vertex is called the MEDIAN.
5.The point where the three medians of a triangle meet,
is called CENTROID. The centroid divides each of the
medians in the ratio 2:1
6.In an isosceles triangle, the altitude from the
vertex bisects the base
7.The median of a triangle divides it into two triangles
of the same area.
8.The area of the triangle formed by joining the mid points
of the sides of a given triangle is one-fourth of the area
of the given triangle.
Results On Quadrilaterals
1.The diagonals of a Parallelogram bisect each other.
2.Each diagonal of a Parallelogram divides it into two
triangles of the same area.
3.The diagonals of a Rectangle are equal and bisect
each other
4.The diagonals of a Square are equal and bisect each
other at right angles.
5.The diagonals of a Rhombus are unequal and bisect
each other at right angles.
6.A Parallelogram and a Rectangle on the same base
and between the same parallels are equal in area.
7.Of all he parallelogram of given sides the parallelogram
which is a rectangle has the greatest area.
Formula
1. Area of a RECTANGLE = length * breadth
Length = (Area/Breadth) and Breadth = (Area/Length)
2. Perimeter of a RECTANGLE = 2(Length + Breadth)
3. Area of a SQUARE = (side)2 = ½ ( Diagonal)2
4. Area of four walls of a room = 2(length + breadth) * height
5. Area of a TRIANGLE = ½ * base * height
6. Area of a TRIANGLE = √s * (s-a) * (s-b) * (s-c)],
where a,b,c are the sides of the triangle and s = 1/2(a+b+c)
7. Area of EQUILATERAL TRIANGLE = √(3/4)* (side)2
8. Radius of in circle of an EQUILATERAL TRIANGLE of
side a = r / 2√3
9. Radius of circumcircle of an EQUILATERAL TRIANGLE
of side a = r / √3
10 Radius of incircle = (a+b-c)/2
11. Area of a PARALLELOGRAM = (base * height)
12. Area of RHOMBUS = 1/2 (product of diagonals)
13. Area of TRAPEZIUM =
=1/2 * (sum of parallel sides)*(distance between them)
14. Area of a CIRCLE = 2 π r where r is the radius
15. Circumference of a CIRCLE = 2 π r
16. Length of an arc = 2 πr/ 360
17. Area of a SECTOR = ½ (arc * r) = π r2 / 360
18. Area of a SEMICIRCLE = 1/2 π r2
19. Circumference of a SEMICIRCLE = π r
