Given 2 vectors: a = ax i + ay j + az k and b = bx i + by j + bz k, which of the following gives the correct expression for the magnitude of the resultant vector r = a × b?
1) r = sqrt((ax × bx)² + (ay × by)² + (az × bz)²)
2) r = sqrt((ax + bx)² + (ay + by)² + (az + bz)²)
3) r = sqrt((ax - bx)² + (ay - by)² + (az - bz)²)
4) r = sqrt((ax × bx) + (ay × by) + (az × bz))