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maths (circle)

• Vectors
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發問:

http://www.fopix.net/d/942492-2/C.jpg Find the radius of the circle. 更新: SORRY~~ ABC is a triangle inscribed in a circle. If AC=BC=15cm and AB =6cm. Length of CN =6√6

最佳解答:

The (circumscribed) circle passing through the three vertices of any triangle with sides a,b,c and area K is given by R=abc/4K=15*15*6/(4*sqrt(1944)=25*sqrt(6)/8=7.6546... To find the area: if a,b, c are the sides of a triangle, and s=(a+b+c)/2, The area of an inscribed circle is given by K=sqrt(s(s-a)(s-b)(s-c)) For a=15,b=15,c=6, s=(15+15+6)/2=18 K=sqrt(18*3*3*12)=sqrt(1944) Alternatively, we can calculate from the traditional formula K=base*height/2=6*6*sqrt(6)=sqrt(1944)

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