Let u v be two vectors in the inner product space R15 with r
Let u, v be two vectors in the inner product space R^15 with respect to the usual dot product. Suppose u · v = 0, ||u|| = 7, ||v|| = 2. Then what is the value of ||2u v||?
A. 4
B. 2 2
C. 4 2
D. 4 3
E. None of the above
Solution
|| 2u -v||
= sqrt ( (2u-v) . (2u-v) )
= sqrt( 2u.2u - 2u.v -2u.v + v.v)
= sqrt(4 || u ||^2 + || v||^2 )
= sqrt ( 4 *7 + 4)
= sqrt(32)
= 4 * sqrt(2)
so the correct choice is C
