Given a > b > C, a + B + C = 1, A2 + B2 + C2 = 1, (1) find the range of a + B, (2) find the range of A2 + B2

Given a > b > C, a + B + C = 1, A2 + B2 + C2 = 1, (1) find the range of a + B, (2) find the range of A2 + B2

AB + AC + BC = 0.5 [(a + B + C) ² - (A & #178; + B & #178; + C & #178;)] = 0, so AB = - (a + b) C = - (1-C) C and because a + B = 1-C, so a and B are two different real roots of the equation x & #178; - (1-C) x - (1-C) C = 0 △ = (1-C) ² + 4 (1-C) C = (1-C) (1 + 3C) > 0, so - 1 / 3 < C