Sunday, August 28, 2016

Vector parallelogram theorem

         If two given incline vectors can be represented by two adjecent line of a parallelogram.(In a diverging manner)the result is given by diagonal after completing the parallelogram.
Deriving the vector parallelogram theorem eqation

Pythagoras theorem OBDΔ

      OD²+DB² = OB²
      
      OD = OA+AD
  
    
  cosθ = AD                             sinθ = BD                                 
              AB                                        AB
      AD = ABcosθ                          BD = Asinθ
            = Qcosθ                                =  Qsinθ
  
  OA = P 

  OD = P+Qcosθ                       BD = Qsinθ

  OB² = R² = (P+Qcosθ)² + (Qsinθ)²
                =  p² + 2PQcosθ + Q²sin²θ + Q²cos²θ
                =  P² + 2PQcosθ + Q²(sin²θ + cos²θ)
                = P² + 2PQcosθ + Q²

  tanα = BD  =  Qsinθ     
          = OD  =  P+Qcosθ

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