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

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

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

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

In any Delta ABC, prove that: (cos^(2)((A)/(2)))/(a)+(cos^(2)((B)/(2)))/(b)+(cos^(2)((c)/(2)))/(c)=(s^(3))/(abc)

In DeltaABC , prove that: (b+c)cos(B+C)/(2)=acos(B-C)/(2)

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