Question Number 16748 by Tinkutara last updated on 26/Jun/17
$$\mathrm{Let}\:{H}\:\mathrm{be}\:\mathrm{orthocenter}\:\mathrm{of}\:\Delta{ABC}\:\mathrm{and}\:{O} \\ $$$$\mathrm{its}\:\mathrm{circumcenter}.\:\mathrm{Prove}\:\mathrm{that}\:\mathrm{the}\:\mathrm{vectors} \\ $$$$\overset{\rightarrow} {{OA}},\:\overset{\rightarrow} {{OB}},\:\overset{\rightarrow} {{OC}}\:\mathrm{and}\:\overset{\rightarrow} {{OH}}\:\mathrm{satisfy}\:\mathrm{the} \\ $$$$\mathrm{following}\:\mathrm{equality}: \\ $$$$\overset{\rightarrow} {{OA}}\:+\:\overset{\rightarrow} {{OB}}\:+\:\overset{\rightarrow} {{OC}}\:=\:\overset{\rightarrow} {{OH}} \\ $$
Commented by mrW1 last updated on 26/Jun/17
$$\mathrm{it}\:\mathrm{would}\:\mathrm{be}\:\mathrm{a}\:\mathrm{great}\:\mathrm{help}\:\mathrm{when}\:\mathrm{you} \\ $$$$\mathrm{post}\:\mathrm{a}\:\mathrm{question}\:\mathrm{as}\:\mathrm{well}\:\mathrm{as}\:\mathrm{the}\:\mathrm{diagram} \\ $$$$\mathrm{to}\:\mathrm{it}\:\mathrm{if}\:\mathrm{available}. \\ $$
Commented by mrW1 last updated on 26/Jun/17
$$\mathrm{I}\:\mathrm{don}'\mathrm{t}\:\mathrm{mean}\:\mathrm{special}\:\mathrm{questions}.\:\mathrm{It}\:\mathrm{is} \\ $$$$\mathrm{generally}\:\mathrm{helpful}\:\mathrm{if}\:\mathrm{diagram}\:\mathrm{could}\:\mathrm{also} \\ $$$$\mathrm{be}\:\mathrm{posted}\:\mathrm{together}\:\mathrm{with}\:\mathrm{the}\:\mathrm{question}. \\ $$