24/05/07 20:30:48.09 OgbPgxVI.net
>>921
θ/2 方向の単位ヴェクトルをｅとすると、
↑OA・ｅ = R cos(60°－θ/2) = R sin((60°+θ)/2) = BQ/2,
↑OB・ｅ = R cos(60°+θ/2) = R sin((60°－θ)/2) = AQ/2,
↑OC・ｅ = －R cos(θ/2) = －R sin(90°－θ/2) =－CQ/2,
辺々たすと
∴ 0 = AQ + BQ －CQ,
∴ AQ + BQ + CQ = 2CQ.