((iv))(a^(2)-b^(2))/(cos A+cos B)+(b^(2)-c^(2))/(cos B+cos C)+(c^(2)-a^(2))/(cos C+cos A)=0

b(cos A-a cos C)=c^(2)-a^(2)

In any triangle ABC, prove that : (a^2-b^2)/(cos A+cos B)+(b^2-c^2)/(cos B+cos C)+(c^2-a^2) /(cos C+cos A)=0 .

(v) (b^(2)-c^(2))/(cos B + cos C) + (c^(2)-a^(2))/( cos C + cosA) + (a^(2)-b^(2))/(cos A + cos B)=0

In /_ABC prove that (b^(2)-c^(2))/(cos B+cos C)+(c^(2)-a^(2))/(cos C+cos A)+(a^(2)-b^(2))/(cos A+cos B)=0

In any Delta ABC, prove that :(b^(2)-c^(2))/(cos B+cos C)+(c^(2)-a^(2))/(cos C+cos A)+(a^(2)-b^(2))/(cos A+cos B)=0

If any triangle ABC, that: (b^(2)-c^(2))/(cos B+cos C)+(c^(2)-a^(2))/(cos C+cos A)+(a^(2)-b^(2))/(cos A+cos B)=0

(b^(2)-c^(2))/(a)cos A+(c^(2)-a^(2))/(b)cos B+(a^(2)-b^(2))/(c)cos C=0

(vii) (b^(2) -c^(2)) cos 2A + (c^(2) -a^(2)) cos 2B + (a^(2) -b^(2)) cos 2C=0

In any DeltaABC , prove that : (b^2 - c^2)/(cos B + cos C) + (c^2 - a^2)/(cos C + cos A) + (a^2 - b^2)/(cos A + cos B) = 0

a(cos C-cos B)=2(b-c)cos^(2)(A)/(2)