If `A,B,C` are the interior angles of a triangle then prove that
`cos(B+C)=-cosA`

If A,B,C are the angles of a triangle then prove that cos A+cos B-cos C=-1+4cos((A)/(2))cos((B)/(2))sin((C)/(2))

If A,B,C are the interior angles of a triangle ABC, prove that (tan(B+C))/(2)=(cot A)/(2)

If A,B,C are the interior angles of a triangle ABC, prove that tan((C+A)/(2))=(cot B)/(2)( ii) sin((B+C)/(2))=(cos A)/(2)

If A,B and C are the interior angles of a triangle ABC, then show that cot((A+B-C)/(2))=tan C

If A,B and C are the interior angles of a triangle ABC, then show that cot((A+B-C)/(2))=tan C

if A, B and C are interior angles of a triangle ABC, then show that cos((B+C)/2) = sin (A/2)

If A,B and C are interior angles of a triangle ABC, then show that sin((B+C)/(2))=cos(A)/(2)

If A, B, C are interior angles of DeltaABC , the prove that cosec((A+B)/2)=sec(C/2) .