07/06/18 00:26:37
>15
[C.847]
面積を ⊿ とおくと、
r=⊿/s, 4R = 2a/sin(A) =abc/⊿,
(⊿^2)/s = (s-a)(s-b)(s-c) (← ヘロン)
より
(左辺) = (r^2･s)^(1/3) = {(⊿^2)/s}^(1/3) = {(s-a)(s-b)(s-c)}^(1/3),
(中辺) = √{(4R+r)r /3} = √{[abc + (⊿^2)/s] /(3s)} = √{[(s-a)(s-b)+(s-b)(s-c)+(s-c)(s-a)] /3},
(右辺) = s /3 = {(s-a) + (s-b) + (s-c)} /3.
以下ry)
まとめ
[C.844] >>41 [C.846] >>48 [C.847] ↑ [C.851] >>41 [C.854] >>50, >>56 [M.1769] >>70
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