Engineering
Mathematics
Vector Triple Product
Question

Let a→,b→  and  c→  be three unit vectors and p→,q→,r→  be three vectors such that p→=(a→⋅b→) a→−b→,  q→=(b→⋅c→) b→−c→  and  r→=(c→⋅a→) c→−a→ . If a→+b→+c→=0,

then which of the following is/are correct ?

|p→|  =  |a→×b→|

p→  + q→ +  r→=0

[p→  q→  r→]=0

[a→   b→   c→]=0

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Solution

p→=a→×(a→×b→)

⇒  |p→|=|a→×b→|

⇒  a→,b→,c→ are coplanar

⇒  p→,q→,r→ are coplanar