This question is in fact a meta question. I have less than 5 points of reputation on meta. So I can not ask this question on the meta.math.stackexchange.com. It reports: "You must have at least 5 reputation on to ask a question." I ask to migrate this question to meta.
Can a simple question: "Demonstrate with vectors that the sum of two vectors of equal modulus [length of vector], which phase changes between 0 and 180 degrees from each other, the square thereof increases from 0 to 4 times the vector length, and the phase will change from 0 to 90 degrees." be on-topic ?
And on the other hand, as in:
be off topic, although tagged ‘physics’ ?
If one consider: https://docs.google.com/file/d/0B7YJn_sAk1ZLSkR4eUt2Tk5fMUE/edit
It provide details.
Is it in that context less off-topic ?