# Math Help - vector question

1. ## vector question

Show that the magnitude of a vector u is equal to (u x u)^1/2

If a x b = a x c, does a = b? Justify your answer.

2. Show that the magnitude of a vector u is equal to (u x u)^1/2
I think you mean the square root of the dot product rather than the cross product ...

$|\vec{u}| = (\vec{u} \cdot \vec{u})^{\frac{1}{2}}$

If a x b = a x c, does a = b? Justify your answer.
are you sure the statement isn't
"If a x b = a x c, does b = c ?"

3. Originally Posted by blague
Show that the magnitude of a vector u is equal to (u x u)^1/2

Mr F says: Apply the basic definition of the dot (scalar) product to u.u ....

If a x b = a x c, does a = b? Justify your answer.

Mr F says: a x b = a x c => a x b - a x c = 0 => a x (b - c) = 0 .....
..