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发表于 2019-4-8 18:45:11
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对于一般三角形,若存在内点P及三条分割线圆弧\(\widehat{AP},\widehat{BP},\widehat{CP}\)将三角形分成面积相等的三等分,且使其分割线总长最小,根据mathe得到的条件:
设\(A[x_1,y_1],B[x_2,y_2],C[x_3,y_3],P[x_0,y_0]\),取\(x_2=0,y_2=0,x_3=a,y_3=0\),三角形三边长及面积为\(a,b,c,s\),三条分割线半径及圆弧角\(r_1,r_2,r_3,2t_1,2t_2,2t_3\),
线段长\(AP=x,BP=y,CP=z\)
则有下列方程:
\(\sin(t_1)yz+\sin(t_2)xz+\sin(t_3)xy=0\)
\(12ay_0\sin(t_2)^2\sin(t_3)^2-3y^2\sin(2t_2)\sin(t_3)^2+3z^2\sin(2t_3)\sin(t_2)^2-8s\sin(t_2)^2\sin(t_3)^2-6z^2t_3\sin(t_2)^2+6y^2t_2\sin(t_3)^2=0\)
\(-6\sin(t_1)^2\sin(t_2)^2a^2y_0+6\sin(t_1)^2\sin(t_2)^2b^2y_0-6\sin(t_1)^2\sin(t_2)^2c^2y_0-3x^2\sin(2t_1)\sin(t_2)^2a+3y^2\sin(2t_2)\sin(t_1)^2a-8s\sin(t_1)^2\sin(t_2)^2a+24x_0s\sin(t_1)^2\sin(t_2)^2-6y^2t_2\sin(t_1)^2a+6x^2t_1\sin(t_2)^2a=0\)
\(\sin(t_1)a^2yz-2\sin(t_1)yzx_0a-\sin(t_1)b^2yz+\sin(t_1)c^2yz-2\sin(t_2)xzx_0a+2\sin(t_3)xya^2-2\sin(t_3)xyx_0a+2\cos(t_1)yzy_0a+2\cos(t_2)xzy_0a+2\cos(t_3)xyy_0a-4\cos(t_1)yzs=0\)
\(2\sin(t_1)xyy_0a+2\sin(t_1)yzy_0a+2\sin(t_2)xzy_0a-\cos(t_1)a^2yz+2\cos(t_1)yzx_0a+\cos(t_1)b^2yz-\cos(t_1)c^2yz+2\cos(t_2)xzx_0a-2\cos(t_3)xya^2+2\cos(t_3)xyx_0a-4\sin(t_1)xys-4\sin(t_1)yzs=0\)
\(-x_0^2+y^2-y_0^2=0\)
\(-a^2+2ax_0-x_0^2-y_0^2+z^2=0\)
\(a^2x_0-ac^2+ax^2-ax_0^2-ay_0^2-b^2x_0+c^2x_0+4sy_0=0\)
取\(a=5,b=4,c=3,s=6\)得到
- sin(t1)*y*z+sin(t2)*x*z+sin(t3)*x*y, 60*y0*sin(t2)^2*sin(t3)^2-3*y^2*sin(2*t2)*sin(t3)^2+3*z^2*sin(2*t3)*sin(t2)^2-48*sin(t2)^2*sin(t3)^2-6*z^2*t3*sin(t2)^2+6*y^2*t2*sin(t3)^2, -108*sin(t1)^2*sin(t2)^2*y0-15*x^2*sin(2*t1)*sin(t2)^2+15*y^2*sin(2*t2)*sin(t1)^2-240*sin(t1)^2*sin(t2)^2+144*x0*sin(t1)^2*sin(t2)^2-30*y^2*t2*sin(t1)^2+30*x^2*t1*sin(t2)^2, 18*sin(t1)*y*z-10*sin(t1)*y*z*x0-10*sin(t2)*x*z*x0+50*sin(t3)*x*y-10*sin(t3)*x*y*x0+10*cos(t1)*y*z*y0+10*cos(t2)*x*z*y0+10*cos(t3)*x*y*y0-24*cos(t1)*y*z, 10*sin(t1)*x*y*y0+10*sin(t1)*y*z*y0+10*sin(t2)*x*z*y0-18*cos(t1)*y*z+10*cos(t1)*y*z*x0+10*cos(t2)*x*z*x0-50*cos(t3)*x*y+10*cos(t3)*x*y*x0-24*sin(t1)*x*y-24*sin(t1)*y*z, -x0^2+y^2-y0^2, -x0^2-y0^2+z^2+10*x0-25, 5*x^2-5*x0^2-5*y0^2+18*x0+24*y0-45
复制代码
得不到我们想要的解,谁有兴趣解一下上面的方程组看能否得到非平凡解?
我用maple只得到了下列平凡解:
- {t1 = 0, t2 = t2, t3 = 0, x = 4, x0 = 5, y = 5, y0 = 0, z = 0}, {t1 = 0, t2 = t2, t3 = Pi, x = 4, x0 = 5, y = 5, y0 = 0, z = 0}, {t1 = 0, t2 = t2, t3 = 0, x = 4, x0 = 5, y = -5, y0 = 0, z = 0}, {t1 = 0, t2 = t2, t3 = Pi, x = 4, x0 = 5, y = -5, y0 = 0, z = 0}, {t1 = 0, t2 = t2, t3 = 0, x = -4, x0 = 5, y = 5, y0 = 0, z = 0}, {t1 = 0, t2 = t2, t3 = Pi, x = -4, x0 = 5, y = 5, y0 = 0, z = 0}, {t1 = 0, t2 = t2, t3 = 0, x = -4, x0 = 5, y = -5, y0 = 0, z = 0}, {t1 = 0, t2 = t2, t3 = Pi, x = -4, x0 = 5, y = -5, y0 = 0, z = 0}, {t1 = Pi, t2 = 0, t3 = 0, x = 4, x0 = 5, y = 5, y0 = 0, z = 0}, {t1 = Pi, t2 = 0, t3 = Pi, x = 4, x0 = 5, y = 5, y0 = 0, z = 0}, {t1 = Pi, t2 = 0, t3 = 0, x = 4, x0 = 5, y = -5, y0 = 0, z = 0}, {t1 = Pi, t2 = 0, t3 = Pi, x = 4, x0 = 5, y = -5, y0 = 0, z = 0}, {t1 = Pi, t2 = 0, t3 = 0, x = -4, x0 = 5, y = 5, y0 = 0, z = 0}, {t1 = Pi, t2 = 0, t3 = Pi, x = -4, x0 = 5, y = 5, y0 = 0, z = 0}, {t1 = Pi, t2 = 0, t3 = 0, x = -4, x0 = 5, y = -5, y0 = 0, z = 0}, {t1 = Pi, t2 = 0, t3 = Pi, x = -4, x0 = 5, y = -5, y0 = 0, z = 0}, {t1 = Pi, t2 = Pi, t3 = 0, x = 4, x0 = 5, y = 5, y0 = 0, z = 0}, {t1 = Pi, t2 = Pi, t3 = Pi, x = 4, x0 = 5, y = 5, y0 = 0, z = 0}, {t1 = Pi, t2 = Pi, t3 = 0, x = 4, x0 = 5, y = -5, y0 = 0, z = 0}, {t1 = Pi, t2 = Pi, t3 = Pi, x = 4, x0 = 5, y = -5, y0 = 0, z = 0}, {t1 = Pi, t2 = Pi, t3 = 0, x = -4, x0 = 5, y = 5, y0 = 0, z = 0}, {t1 = Pi, t2 = Pi, t3 = Pi, x = -4, x0 = 5, y = 5, y0 = 0, z = 0}, {t1 = Pi, t2 = Pi, t3 = 0, x = -4, x0 = 5, y = -5, y0 = 0, z = 0}, {t1 = Pi, t2 = Pi, t3 = Pi, x = -4, x0 = 5, y = -5, y0 = 0, z = 0}, {t1 = 0, t2 = Pi, t3 = Pi, x = 0, x0 = 9/5, y = 3, y0 = 12/5, z = 4}, {t1 = 0, t2 = Pi, t3 = Pi, x = 0, x0 = 9/5, y = 3, y0 = 12/5, z = -4}, {t1 = 0, t2 = Pi, t3 = Pi, x = 0, x0 = 9/5, y = -3, y0 = 12/5, z = 4}, {t1 = 0, t2 = Pi, t3 = Pi, x = 0, x0 = 9/5, y = -3, y0 = 12/5, z = -4}, {t1 = Pi, t2 = Pi, t3 = Pi, x = 0, x0 = 9/5, y = 3, y0 = 12/5, z = 4}, {t1 = Pi, t2 = Pi, t3 = Pi, x = 0, x0 = 9/5, y = 3, y0 = 12/5, z = -4}, {t1 = Pi, t2 = Pi, t3 = Pi, x = 0, x0 = 9/5, y = -3, y0 = 12/5, z = 4}, {t1 = Pi, t2 = Pi, t3 = Pi, x = 0, x0 = 9/5, y = -3, y0 = 12/5, z = -4}, {t1 = t1, t2 = 0, t3 = t3, x = 3, x0 = 0, y = 0, y0 = 0, z = 5}, {t1 = t1, t2 = 0, t3 = t3, x = 3, x0 = 0, y = 0, y0 = 0, z = -5}, {t1 = t1, t2 = 0, t3 = t3, x = -3, x0 = 0, y = 0, y0 = 0, z = 5}, {t1 = t1, t2 = 0, t3 = t3, x = -3, x0 = 0, y = 0, y0 = 0, z = -5}, {t1 = t1, t2 = Pi, t3 = t3, x = 3, x0 = 0, y = 0, y0 = 0, z = 5}, {t1 = t1, t2 = Pi, t3 = t3, x = 3, x0 = 0, y = 0, y0 = 0, z = -5}, {t1 = t1, t2 = Pi, t3 = t3, x = -3, x0 = 0, y = 0, y0 = 0, z = 5}, {t1 = t1, t2 = Pi, t3 = t3, x = -3, x0 = 0, y = 0, y0 = 0, z = -5}, {t1 = 0, t2 = 0, t3 = t3, x = 0, x0 = 9/5, y = 3, y0 = 12/5, z = 4}, {t1 = 0, t2 = 0, t3 = t3, x = 0, x0 = 9/5, y = 3, y0 = 12/5, z = -4}, {t1 = 0, t2 = 0, t3 = t3, x = 0, x0 = 9/5, y = -3, y0 = 12/5, z = 4}, {t1 = 0, t2 = 0, t3 = t3, x = 0, x0 = 9/5, y = -3, y0 = 12/5, z = -4}, {t1 = Pi, t2 = 0, t3 = t3, x = 0, x0 = 9/5, y = 3, y0 = 12/5, z = 4}, {t1 = Pi, t2 = 0, t3 = t3, x = 0, x0 = 9/5, y = 3, y0 = 12/5, z = -4}, {t1 = Pi, t2 = 0, t3 = t3, x = 0, x0 = 9/5, y = -3, y0 = 12/5, z = 4}, {t1 = Pi, t2 = 0, t3 = t3, x = 0, x0 = 9/5, y = -3, y0 = 12/5, z = -4}, {t1 = 0, t2 = t2, t3 = 0, x = 0, x0 = 9/5, y = 3, y0 = 12/5, z = -4}, {t1 = 0, t2 = t2, t3 = 0, x = 0, x0 = 9/5, y = 3, y0 = 12/5, z = 4}, {t1 = 0, t2 = t2, t3 = 0, x = 0, x0 = 9/5, y = -3, y0 = 12/5, z = 4}, {t1 = 0, t2 = t2, t3 = 0, x = 0, x0 = 9/5, y = -3, y0 = 12/5, z = -4}, {t1 = Pi, t2 = t2, t3 = 0, x = 0, x0 = 9/5, y = 3, y0 = 12/5, z = 4}, {t1 = Pi, t2 = t2, t3 = 0, x = 0, x0 = 9/5, y = -3, y0 = 12/5, z = -4}, {t1 = Pi, t2 = t2, t3 = 0, x = 0, x0 = 9/5, y = -3, y0 = 12/5, z = 4}, {t1 = Pi, t2 = t2, t3 = 0, x = 0, x0 = 9/5, y = 3, y0 = 12/5, z = -4}
复制代码
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