In triangle ABC with sides a,b,c and semiperimzeter s，prove

If a, b,c are 3 side of △ABC中 such that (b+c):(c+a):(a+b) = 4:5:6, then the maximum internal angle of △ABC is

Let a, b, c be the three sides of a triangle △ABC, If the area S and the sides satisfy S = a^2-(b -c)^2 , and b+c = 8, find the maximum value of S

Given a triangle △ABC with AC=17 , BC=14 and

∠ACB=60 , find the value of AB .

If a triangle has three sides with length of 9,7,6. What is measure of the internal angle α between the sides of 9, 6?