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\title{Tangente 3}
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\range{-5,5}
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\real{a = random(-1,1)*randint(1..30)/10}
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\real{b = randint(-20..20)/10}
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\real{c = randint(-20..20)/10}
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\function{f = \a*x^2+simplify(\b*x) + \c}
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\real{x0 = randint(-40..40)/10}
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\real{y0 = evalue(\f, x = \x0)}
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\function{df = diff(\f,x)}
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\real{df0 = evalue(\df,x = \x0)}
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\function{D = \df0*x - simplify(\df0*\x0 - \y0)}
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\integer{xmin = min(-3, \x0 - 2)}
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\integer{xmax = max(3, \x0 + 2)}
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\text{A = slib(function/bounds \f, x,\xmin,\xmax)}
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\integer{ymin = min(-3, \A[1] - 2)}
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\integer{ymax = max(3, \A[2] + 2)}
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\text{rangex = \xmin, \xmax}
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\text{rangey = \ymin, \ymax}
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\text{dessin = rangex \rangex
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  rangey \rangey
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  arrow \xmin,0,\xmax,0,10, black
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  arrow 0,\ymin,0,\ymax,10, black
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  plot navy,\f
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  circle \x0,\y0,5, red
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  text black,0,0,roman,0
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}
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\text{url = draw(200,200
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  \dessin)}
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\text{dessinc = \dessin
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 plot green,\D
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}
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\text{urlc = draw(200,200
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  \dessinc)}
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\real{x1 = \x0+1}
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\real{y1 = \df0*\x1 - \df0*\x0 + \y0}
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\text{P0 = slib(draw/convpixel \x0,\y0,200,200,\rangex,\rangey,0,pixels)}
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\text{P1 = slib(draw/convpixel \x1,\y1,200,200,\rangex,\rangey,0,pixels)}
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\text{rep = \url;line,\P0[1],\P0[2],\P1[1],\P1[2]}
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\statement{En utilisant la souris, positionner la  tangente
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 à la courbe d'équation \(y = \f\) au point  d'abscisse \x0.
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<div class="wims_instruction">
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NB : le tracé sera obtenu en définissant deux points
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 appartenant à cette tangente.
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</div>
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<div class="wimscenter">\embed{reply1,200x200}</div>
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}
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\answer{}{\rep}{type=jsxgraphcurve}
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\text{dessinc = \dessin
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 plot green,\D
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}
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\solution{La droite tangente au point d'abscisse \x0 est dessinée en vert :
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<p class="wimscenter"><img src="\urlc" alt=""></p>
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}