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Motion In A Plane

Question
CBSEENPH11018347

Show that if two adjacent sides of parallelogram represent the two vectors, then area of the parallelogram is equal to magnitude of the cross product of two vectors. 

Solution

As shwn in the fig., et PQRS be a parallelogram formed by vectors straight A with rightwards arrow on top space and space straight B with rightwards arrow on top.
               
From the figure,
Area of parallelogram PQRS is given by, 
                S = PQ. RN 
                   = PQ. space PR space sinθ space equals space straight A space straight B space sinθ 
                 space space equals open vertical bar straight A with rightwards arrow on top cross times straight B with rightwards arrow on top close vertical bar 
Hence the result.