算額(その353)
二十九 群馬県高崎市山名町 八幡宮 文化11年(1814)
群馬県和算研究会:群馬の算額,上武印刷株式会社,高崎市,1987年3月31日.
群馬県高崎市山名町 山名八幡宮 文化11年(1814)
http://takasakiwasan.web.fc2.com/gunnsann/g029-4.html
キーワード:円4個,直角三角形
鈎股弦(直角三角形)内に,大円 1 個と小円 3 個を入れる。鈎の長さが 3 寸のとき,股の長さはいかほどか。
include("julia-source.txt");
using SymPy
@syms 鈎::positive, 股::positive, x1::positive, r1::positive,
r2::positive, x2::positive, y2::positive;
鈎 = 3
eq1 = (x1 - r2)^2 + (r1 - r2)^2 - (r1 + r2)^2
eq2 = (x1 - r2)^2 + (3r2 - r1)^2 - (r1 + r2)^2
eq3 = (x1 - x2)^2 + (y2 - r1)^2 - (r1 + r2)^2
eq4 = (x2 - r2)^2 + (y2 - 3r2)^2 - 4r2^2
eq5 = distance(0, 鈎, 股, 0, x1, r1) - r1^2
eq6 = distance(0, 鈎, 股, 0, x2, y2) - r2^2;
# solve([eq1, eq2, eq3, eq4, eq5, eq6]);
using NLsolve
function nls(func, params...; ini = [0.0])
if typeof(ini) <: Number
r = nlsolve((vout, vin) -> vout[1] = func(vin[1], params..., [ini]), ftol=1e-14)
v = r.zero[1]
else
r = nlsolve((vout, vin)->vout .= func(vin, params...), ini, ftol=1e-14)
v = r.zero
end
return v, r.f_converged
end;
function H(u)
(股, r1, x1, r2, x2, y2) = u
return [
(r1 - r2)^2 - (r1 + r2)^2 + (-r2 + x1)^2, # eq1
(-r1 + 3*r2)^2 - (r1 + r2)^2 + (-r2 + x1)^2, # eq2
(-r1 + y2)^2 - (r1 + r2)^2 + (x1 - x2)^2, # eq3
-4*r2^2 + (-3*r2 + y2)^2 + (-r2 + x2)^2, # eq4
-r1^2 + (r1 - 3*(3*r1 - x1*股 + 股^2)/(股^2 + 9))^2 + (x1 - 股*(-3*r1 + x1*股 + 9)/(股^2 + 9))^2, # eq5
-r2^2 + (x2 - 股*(x2*股 - 3*y2 + 9)/(股^2 + 9))^2 + (y2 - 3*(-x2*股 + 3*y2 + 股^2)/(股^2 + 9))^2, # eq6
]
end;
iniv = [big"4.0", 1, 2, 0.5, 1.2, 2]
res = nls(H, ini=iniv);
股 = 3.71231; r1 = 0.782752; x1 = 1.49835; r2 = 0.391376; x2 = 0.883366; y2 = 1.78293
using Plots
function draw(more)
pyplot(size=(500, 500), grid=false, aspectratio=1, label="", fontfamily="IPAMincho")
鈎 = 3
(股, r1, x1, r2, x2, y2) = res[1]
@printf("股 = %g; r1 = %g; x1 = %g; r2 = %g; x2 = %g; y2 = %g\n", 股, r1, x1, r2, x2, y2)
plot([0, 股, 0, 0], [0, 0, 鈎, 0], color=:black, lw=0.5)
circle(x1, r1, r1, :blue)
circle(r2, r2, r2)
circle(r2, 3r2, r2)
circle(x2, y2, r2)
if more
delta = (fontheight = (ylims()[2]- ylims()[1]) / 500 * 10 * 2) /3 # size[2] * fontsize * 2
point(x1, r1, "大円:r1,(x1, r1)", :blue, :center, delta=-delta)
point(r2, r2, "小円:r2\n(r2,r2)", :green, :center, delta=-delta)
point(r2, 3r2, "(r2,3r2)", :red, :center, delta=-delta)
point(x2, y2, "(x2,x2)", :red, :center, delta=-delta)
point(股, 0, " 股", :black, :left, :bottom)
point(0, 鈎, " 鈎", :black, :left, :bottom)
hline!([0], color=:black, lw=0.5)
vline!([0], color=:black, lw=0.5)
else
plot!(showaxis=false)
end
end;
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