Let O be the origin, and −−→OX,−−→OY,−−→OZ be three unit vectors in the directions of the sides −−→QR,−−→RP,−−→PQ, respectively, of a triangle PQR.If the triangle PQR varies, then the minimum value of cos(P+Q)+cos(Q+R)+cos(R+P)

Let O be the origin, and −−→OX,−−→OY,−−→OZ be three

1.	Let O be the origin, and −−→OX,−−→OY,−−→OZ be three unit vectors in the directions of the sides −−→QR,−−→RP,−−→PQ, respectively, of a triangle PQR.If the triangle PQR varies, then the minimum value of cos(P+Q)+cos(Q+R)+cos(R+P)
Answer» Let $O$ be the origin, and $- - \to O X, - - \to O Y, - - \to O Z$ be three unit vectors in the directions of the sides $- - \to Q R, - - \to R P, - - \to P Q,$ respectively, of a triangle $P Q R .$ If the triangle $P Q R$ varies, then the minimum value of $cos (P + Q) + cos (Q + R) + cos (R + P)$