放物線の接線 - DyGeom.m on Mathematica+KETpic

(* ver 0.30 以降 in Japanese*)
SetDirectory[NotebookDirectory[]];
<< ketpic6.m　(* Mathematica 6 だと必要です。*)
<< DyGeom.m
MyAxes = True;
MyPolynomialCalculation = True;
f = グラフ[x^2, {x, -3, 3}, target -> {-1.5, 4}]
p1 = グラフ上の点[f, 1.5]
p2 = グラフ上の点[f, -1]
l1 = グラフの接線[f, p1]
l2 = グラフの接線[f, p2]
p3 = 交点[l1, l2]
p4 = 中点[p1, p2]
l3 = 線分[p1, p2]
l4 = 線分[p3, p4]
b1 = カッコ印[p1, p4, bowshape -> "dash"]
b2 = カッコ印[p4, p2, bowshape -> "dash"]
作図[f, p1, p2, l1, l2, l3, l4, p3, p4, b1, b2]

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数式処理のほうを良く見ると、直線l4がy軸平行であることが代数計算によって示されています。

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(* ver 0.30~ in English*)
SetDirectory[NotebookDirectory[]];
<< ketpic6.m
<< DyGeom.m
MyAxes = True;
MyPolynomialCalculation = True;
f = FunctionGraph[x^2, {x, -3, 3}, target -> {-1.5, 4}]
p1 = PointOnFunctionGraph[f, 1.5]
p2 = PointOnFunctionGraph[f, -1]
l1 = TangentLineOnGraph[f, p1]
l2 = TangentLineOnGraph[f, p2]
p3 = GeomIntersection[l1, l2]
p4 = MidPoint[p1, p2]
l3 = ConnectPoints[p1, p2, clipping -> {p1, p2}]
l4 = ConnectPoints[p3, p4, clipping -> {p3, p4}]
b1 = BowMark[p1, p4, bowshape -> "dash"]
b2 = BowMark[p4, p2, bowshape -> "dash"]

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