Today we are going to talk about the some Important arithmetic formulae on polygon , circles , Room and sector & segment. Here you can access list of all the formulae at one place.

Students are advised to learn all the formulae and keep practicing with it.

**SOME IMPORTANT SUTRAS**

** POLYGON*1). Each internal angle of the regular polygon =

180(n-2)/n

2). Perimeter of regular polygon = n×a

3). Perimeter of regular hexagons = 6×sides

4). Area of regular hexagons = (6√3/4)×side^2

5). Sum of all the internal angles of n sided polygon = 180(n-2)

6). Every external angle of n sided regular polygon = 360/n

7). Area of regular polygon = n×a×h/2

8). Areas of regular polygon = na^2.cot(π/2)/4

9). Length of the perpendicular drawn from the centre of the regular polygon to the side is =

a.tan(θ/2)/2

10). Length of the perpendicular drawn from the centre of the regular polygon to the side is =

a.cot(π/n)/2

11). No of diagonals of n sided regular polygon =

n(n-3)/2

** CIRCLES*1). Area of circles = πr^2

2). Area of circles = πd^2/4

3). Area of semicircle = πr^2/2

4). Radius of circle = √A/π

5). Circumference of circle = 2πr = πd

6). Radius of circle = circumference/2π

7). Diameter of circle = circumference/π

8). Circumference of semicircle = (π+2).r

9). Area of flat rings = π(R^2-r^2)

10). Area of biggest triangle formed in the semicircle of radius r = r^2

** ROOMS*1). Area of the surface of the room = l.b

2). Area of four wall = 2(l+b).h

3). Area of room’s roof = l.b

4). No. Of bricks = l×b/area of one bricks

5). Cost of area = area×cost of unit area

6). Area = total cost/cost per unit

** SECTOR & SEGMENT*1). Area of sector = πr^2θ/360

2). Area of sector = l×r/2

3). Length of arc = 2πrθ/360

4). Perimeter of sector = 2πrθ/360 + 2r

5). Angle of the sector = 360×A/πr^2

6). Area of major segment =

πr^2.(360-θ)+r^2.sinθ/2

7). Area of minor segment =

πr^2.θ/360-r^2.sinθ/2

8). Perimeter of minor segment =

2πr.θ/360+2r.sinθ/2

9). The largest side of square in the circle = √2.r

10). Area of the largest square in the circle = 2r^2

= D^2/2

11). Area of major sector = πr^2(360-θ)/360