" In "Delta ABC" ,if "b+c:c+a:a+b=11:12:13" then "cos A:cos B:cos C=

In Delta ABC,a(b cos C-c cos B)=

With usual notation,in Delta ABC (b+c)/(11)=(c+a)/(12)=(a+b)/(13) then cos A:cos B:cosC 1. 7:19:25 2. 19:25:7, 3 19:7:25 4. 7:25:19

In Delta ABC , a( b cos C - c cos B) =

In a triangle ABC, cos A+cos B+cos C=

In a triangle ABC, cos A+cos B+cos C=

In Delta ABC, cos A + cos (B-C)=

In Delta ABC, prove that :(c-b cos A)/(b-c cos A)=(cos B)/(cos C)

In Delta ABC, (b-a cos C)/(c-a cos B)=

With usual notation , if in triangle ABC, (b + c)/11 = (c + a)/12 = (a + b)/13 , then cos A : cos B : cos C =