The direction of \(\vec \nabla f\) for a scalar field f(x, y , z) = \(\rm \frac{1}{2}x^2-xy+\frac{1}{2}z^2\) at the point P (1, 1, 2) is
1
\(\rm \frac{(-\hat j-2\hat k)}{\sqrt5}\)
2
\(\rm \frac{(-\hat j+2\hat k)}{\sqrt5}\)
3
\(\rm \frac{(\hat j-2\hat k)}{\sqrt5}\)
4
\(\rm \frac{(\hat j+2\hat k)}{\sqrt5}\)