In any `DeltaABC` prove by vectors that `b^2=c^2+a^2-2` ca `cos` B.

In any DeltaABC prove by vectors that a^2=b^2+c^2-2 bc cos A.

In any triangle ABC, then by vectors, prove that : c^2=a^2+b^2-2ab cos C .

In DeltaABC, prove that cosA=(b^2+c^2-a^2)/(2b c) by vector method.

In any triangle ABC, then by vectors, prove that : a=b cos C+c cos B .

In any triangle ABC, prove that cos A= frac{b^2+c^2-a^2}{2bc} .

In any triangle ABC, prove that : (b^2-c^2) cot A + (c^2-a^2)cot B +(a^2-b^2)cotC=0 .

In a triangleABC , prove by vector method that cos2A+cos2B+cos2Cge(-3)/(2) .

In any DeltaABC, 2 [bc cos A + ca cos B+ ab cos C]=

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

In any triangle ABC, prove that : (b^2-c^2)/(a^2)= sin (B -C)/sin(B+C) .