S3N3 Obtuse Angle - SinX and CosX, Sine and Cosine Rule

Extending Sin X and Cos X to Obtuse Angle

     Sin A = Sin (180 - A)

     Cos A = -Cos (180 - A)

Sine Formula

Area of Triangle

Area of  ⃤ ABC 

  = 1/2 ab Sin C 

  = 1/2 bc SinA 

  = 1/2 ac SinB

Area =  √ s(s -a) (s-b) (s - c) where 2s = a + b + c

Sine Rule

            a       =     b     =    c

          SinA        SinB      SinC                 

                         or 

          SinA  =  SinB   =   SinC

             a            b             c

Cosine Rule

             a² = b² + c² – 2bcCosA

             Cos A = b² + c² - a² / 2bc

              Cos B = a² + c² - b² / 2ac

              Cos C = a² + b² - c² / 2ab

Bearing

When reading a compass bearing, the directions are from either north of the south. 

From the North, 060^o is N60^oE

From the South, 225^o is S45^oW

Decimal values are to be included in all compass reading.