# Solution OF Triangle

### Basic Rules :

 In a triangle ABC, the angles are denoted by capital letters A,B, and C and the lengths of the sides opposite to these angles are denoted by small letters a, b, and c respectively. Semi – perimeter of the triangle is written as  s = (a + b + c)/2 and its area denoted by S or Δ .

Sine rule:

, where R is the radius of the circumcircle of the Δ ABC.

Cosine rule:

Projection rule:

a = b cosC + c cosB ,

b = c cosA + a cosC ,

c = a cosB + b cosA

Napier’s analogy :

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