Quandaries and Queries


I am learning about vectors via the web and i am doing a few problems to get familiar with vectors, however i am stuck here.

" a=3i-j+2k and b=i+3j-2k, determine the magnitude and direction cosines of the product vector and show that it is perpendicular to a vector c=9i+2j+2k."

I know if 2 vectors are perpendicular then their dot product is 0 correct? But after that i am stuck on this question.
I would appreciate your help.




Hi Annie,

The teacher wants you to compute a b (the vector product, which is sometimes called the cross product, of the first two), to determine its magnitude and direction cosines, and then to show that the product vector is perpendicular to c. For the final task, you could obtain the same conclusion by showing that c is in the plane of a and b (in fact 5a + 3b = 2c).



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