SSC Tier 2- Some useful Geometry Formulas

As all of you know that gradually SSC is increasing the weightage of the Geometry (See the below table) , thus gaining a prominent place in the maths section. Moreover, because of the complexity and diversity of the problem area  usually it become a tough nut to crack for the aspirants.

But truly speaking with a little bit knowledge of some basic formula one is able to solve easily more than 75% of the problems.

Type	2010	2011	2012
Geometry	14	10	27

Facts about Polygon

Some of all angles of polygon with 'n' side= (2n-4)*90
Sum of Interior and exterior angles of a polygon= I+E=180
Each Exterior angle=360/n
Each Interior angle =180-360/n

Triangle Properties
Assume a Tringle having sides a,b,c where

R= Circum Radius : r= Inradius ; s=(a+b+c)/2  ; A= Area of triangle
Sine Rule     :  a/SinA=b/SinB=c/SinC= 2R
Cosine Rule  :  a2=b2+c2 -2bcCosA
Area             :  1/2 bcSinA             
Important Formula  :  abc/4A=R  and r=A/s  one of the favorite formula of examiners.

For Equilateral Triangle

Area	Height	R	r
Sqrt3/4 side*2	Sqrt3/2 side	Side/Sqrt3	Side/2Sqrt3

OrthoCenter  Meeting point of all altitudes

angle BOC  + angle A = 180 = angle C + angle AOB

Incenter  angle BOC = 1/2 angle A + 90

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