In any `DeltaABC`, prove that
`(cos2A)/a^(2)-(cos2B)/b^(2)=(1/a^(2)-1/b^(2))`

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

In any DeltaABC , prove that (1+cos(A-B)cosC)/(1+cos(A-C)cosB)=(a^(2)+b^(2))/(a^(2)+c^(2))

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

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

In any Delta ABC, prove that :(b^(2)-c^(2))cos2A+(c^(2)-a^(2))cos2B+(a^(2)-b^(2))cos2C=0

In any DeltaABC , prove that a(cosC-cosB)=2(b-c)cos^(2)""1/2A

In any DeltaABC , prove that c^(2)=(a-b)^(2)cos^(2)""1/2C+(a+b)^(2)sin^(2)""1/2C

In any Delta ABC, prove that :(1+cos(A-B)cos C)/(1+cos(A-C)cos B)=(a^(2)+b^(2))/(a^(2)+c^(2))

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