enter image description here

Can someone explain to me what is a meaning of the starred items in this picture?


closed as unclear what you're asking by Bimpelrekkie, PlasmaHH, RoyC, Leon Heller, Dmitry Grigoryev Oct 31 '18 at 8:52

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.


The dot signifies a vector out of the page; the cross signifies a vector into the page.

  • 1
    \$\begingroup\$ In other words, it's a common notation used to describe vectors in three dimensions on 2-D drawings. \$\endgroup\$ – Dave Tweed Oct 30 '18 at 13:39

Not the answer you're looking for? Browse other questions tagged or ask your own question.