Given that \(\vec a=2\hat i-3\hat j+6\hat k\)
The unit vector of any vector \(\vec a=a_1\hat i+a_2\hat j+a_3\hat k\) can be written as
Let the required vector be \(\vec d\).
Any vector ( \(\vec p\)) with magnitude m and unit vector \(\hat a\) can be written as \(\vec p=m\times\hat a.\)
Since the magnitude of \(\vec d\)is 21 and it's unit vector is \(\hat a,\) we get