In any `DeltaABC`, prove that : `a^2 +b^2 +c^2 = 2 (bc cos A + ca cos B + ab cos C)`.

In any DeltaABC , prove that : a cos A + b cos B + c cos C = 2a sin B sin C

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

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)

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

In any A B C ,2(bc cosA+ ca cosB+ab cosC) =

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

In any DeltaABC , prove that (sin B)/(sin C) = (c-a cos B)/(b-a cos C)

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

In any DeltaABC , prove that : (cos A)/a + a/(bc) = (cos B)/b + b/(ca) = (cos c)/c + c/(ab)

In any DeltaABC , prove that asin""1/2(B-C)=(b-c)cos""1/2A