题目

-- We’re organizing a party next Saturday, and I’d like you to come.   -- _______! I have another one that day. Thank you just the same.   A. Good luck!       B. What a pity!       C. Never do it again!    D. Well done! 答案：B的内角所对的边分别为.（1）若成等差数列，证明：；（2）若成等比数列，求的最小值.