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Clash Royale CLAN TAG #URR8PPP up vote -1 down vote favorite The co-ordinates of a point P referred to a rectangular co-ordinate system where O is the origin are $(1,-2)$. The axes are rotated about 0 through angle theta, if coordinates of the new P are $(k-1,k+1)$, then $k^2$? geometry analytic-geometry share | cite | improve this question edited Aug 16 at 11:19 asked Aug 16 at 11:12 Abdullah 1 2 closed as off-topic by Morgan Rodgers, Arnaud D., amWhy, José Carlos Santos, Nosrati Aug 17 at 17:34 This question appears to be off-topic. The users who voted to close gave this specific reason: " This question is missing context or other details : Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience...

Clash Royale CLAN TAG #URR8PPP up vote 0 down vote favorite This question already has an answer here: showing that $n$th cyclotomic polynomial $Phi_n(x)$ is irreducible over $mathbbQ$ 6 answers I have no idea what cyclotomic polynomials are and how we can get the result using that. Is there another way to prove it? Any hint is appreciated. vector-spaces roots-of-unity share | cite | improve this question asked Aug 16 at 11:29 Hrit Roy 837 1 13 marked as duplicate by Dietrich Burde, Lord Shark the Unknown, John Ma, José Carlos Santos, Xander Henderson Aug 17 at 0:01 This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question. @DietrichBurde as I said; we don't know what cyclotomic polynomials are. Our professor asked us this knowing that fact. There must be some other way to prove it. – Hrit Roy Aug 16 a...