hi!
can i know how to prove that the cosine rule is true for ∏/2≤ x ≤∏ for
c^2 = a^2 + b^2 - 2ab cos x?
i want to show that it is true for 0 ≤ x ≤∏ and have proven that it is true for 0≤x≤∏/2 but i dont know how to prove the other part..
thanks!!!