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问题问题146先给出推导三角形外接圆半径的一个方法:设三角形的三条边长分别是a,b,c,而R,s分别是△ABC的外接圆半径及△ABC的半周长,则由三角形的面积公式、正弦定理及海伦公式可以得到S△ABC=21absinC=4abRc=s(s-a)(s-b)(s-c),由此可以得出R=abc4s(s-a)(s-b)(s-c).即知道一个
Problem 146 first gives a method for deriving the radius of a circumcircle of a triangle: Let the three sides of the triangle be a, b, and c, and R and s be the radius of the circumscribed circle of △ABC and the half-circle of △ABC. The area formula of the triangle, the sine theorem, and Helen’s formula can get SΔABC=21absinC=4abRc=s(sa)(sb)(sc), from which R=abc4s(sa)(sb)(sc). know a