engineering recuitment ISRO Scientific Assistant Physics 2020 Engineering Mathematics Calculus Vector Calculus
The directional derivative of 1/r in the direction of \(\vec r\) is
1
\(\frac {1}{r^2}\)
2
\(-\frac {1}{r^2}\)
3
\(\frac {1}{r^3}\)
4
\(-\frac {\vec r}{r^3}\)