If  and   Find a vector  such that  and 

Let  and . Find a vector  which is perpendicular to both 

293. If with reference to a right handed system of mutually perpendicular unit vector unit vector 

express  in the form  in the form 

Let vectors  be such that  then  is a unit vector, if the angle betweeen  is 

If  is the angle between any two vectors  then  when  is equal to 

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