The sides of a triangle are x^(2 )+x+1, 2x+1,x^2-1, prove that the largest angle is 120 degrees, and find range of x. Ans) The biggest side is x^(2) + x + 1so findout the angle opposite to that byCos(A) = (b^2 + c^2-a^2)/2*b*cwhich gives Cos(A) = -1/2 ie 120degress