With usual notatins, if in a Delta ABC,(...

With usual notatins, if in a `Delta ABC,(b+c)/(11)=(c+a)/(12) =(a+b)/(13),` then prove that `(cos A)/(7) =(cos B)/(19) =(cos C)/(25).`

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`(cos A)/(7) =(cos B)/(19)=(cos C)/(25)`

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