The reasoning process of calculating the radius of inscribed circle and circumscribed circle of triangle RT

The reasoning process of calculating the radius of inscribed circle and circumscribed circle of triangle RT

Given that the side lengths of three vertices a, B and C of △ ABC are a, B and C in turn, the area s of △ ABC is s = √ [(a + B + C) (- A + B + C) (a-b + C) (a + B-C)] / 4 according to Helen's formula; if the radius of the inscribed circle of △ ABC is R and the radius of the circumscribed circle is r, then: ∵ s = (AR / 2) + (BR / 2) + (CR / 2), ∧ r = 2S / (a + B + C), that is, r = √ [(...)

The formula of circumscribed circle radius and inscribed circle radius of arbitrary triangle
That's a point

2R=A/SINA=B/SINB=C/SINC
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