22. △ABC 中, ∠A = 105° , ∠B = 45° ,
【用戶】Spade Sentry
【年級】大二下
【評論內容】正弦公式 a/sinA = b/sinB = c/sinC = 2R 〔2*外接圓半徑〕∠C = 30° ,c/sinC = 5/1/2 = 10 = 2R,R = 5 選(B)。