" 5.(a) "a(b cos C-c cos B)=b^(2)-c^(2)" ."

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

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

Prove that: (1+ cos (A-B) cos C)/(1+ cos (A-C) cos B) = (a^(2) +b^(2))/(a^(2) + c^(2))

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

In triangle ABC , prove that (1) a=b cos C+c cos B (2) b=a cos C+c cos A .

(1+cos A*cos(B-C))/(1+cos C*cos(A-B))=(b^(2)+c^(2))/(a^(2)+b^(2))

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

In a Delta ABC if (cos A)/(b cos C+c cos B)+(cos B)/(c cos A+a cos C)+(cos C)/(a cos B+b cos A)=(a^(2)+b^(2)+c^(2))/(Kabc) then K^(k) is equal to

(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