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In the case of a vector, direction is one of the most important components. Without direction, you won't call it a vector, that would be a straight line that has magnitude only. We can find the direction of a vector with the help of cosine. In an orthonormal basis, direction cosines of the vector are:
It is necessary that you should be working on an orthonormal basis otherwise this formula won't be valid.
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Example
Determine the direction cosines of the vector with components .
A vector is drawn on the basis of orthonormal and has components . Find the direction cosines.