Prove that: `cos(A+B+C)+cos(A-B+C)+cos(A+B-C)+cos(-A+B+C)=4cos A\ cos B\ cos C`

if A + B +C= pi/2 ,prove that cos(A - B - C)+ cos (B-C- A) + cos (C- A - B)= 4 cos A cos B cos C

If A + B + C =180^@ , prove that : cos (-A+B +C)+cos(A-B+C)+ cos (A +B-C)=1+ 4cos A cos B cos C .

cos (B+C-A)-cos(C+A-B)+cos(A+B-C)- cos (A+B+C)=

In any DeltaABC , 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)

Prove that cos (A + B) cos C - cos (B + C) cos A = sin B sin (C - A)

In any triangle ABC, prove that following: a(cos B cos C+cos A)=b(cos C cos A+cos B)=c(cos A cos B+cos C)

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 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)

If A + B + C =pi , prove that : cos 2A + cos 2B + cos 2C = -1-4 cos A cos B cos C .