f(x) = If[x > 0, 1 / sqrt(x)]
A = Point(f)
g = Tangent(A, f)
piirto1: PolyLine[(1.8493E-1,1.5744E0), (1.2350E-1,1.4976E0), (6.2064E-2,1.4208E0), (3.1348E-2,1.3440E0), (NaN,NaN), (5.6887E-1,1.3286E0), (4.4601E-1,1.2365E0), (2.6172E-1,1.0829E0), (1.0814E-1,8.9861E-1), (7.7422E-2,8.5254E-1), (NaN,NaN), (6.6102E-1,9.2933E-1), (5.5352E-1,8.3718E-1), (3.8458E-1,6.9896E-1), (1.5421E-1,4.5323E-1), (3.1348E-2,2.8429E-1), (-1.4725E-2,2.0751E-1), (6.2064E-2,2.0751E-1), (NaN,NaN), (1.0603E0,5.9145E-1), (8.1460E-1,3.9180E-1), (5.2280E-1,1.7679E-1), (4.3065E-1,6.9284E-2), (5.2280E-1,6.9284E-2), (NaN,NaN), (1.4596E0,2.9965E-1), (1.3828E0,2.3822E-1), (1.1832E0,8.4642E-2), (1.0757E0,7.8527E-3), (9.9890E-1,-6.8937E-2), (1.1218E0,-6.8937E-2), (NaN,NaN), (1.8589E0,8.4642E-2), (1.7207E0,3.8568E-2), (1.5825E0,-3.8221E-2), (1.5364E0,-6.8937E-2), (NaN,NaN), (7.8388E-1,2.6894E-1), (7.2245E-1,2.3822E-1), (6.1495E-1,1.0000E-1), (5.3816E-1,-1.4573E-1), (5.0744E-1,-3.7609E-1), (5.0744E-1,-5.7575E-1), (5.0744E-1,-7.2933E-1), (5.3816E-1,-9.1362E-1), (5.6887E-1,-1.0672E0), (6.1495E-1,-1.2208E0), (6.6102E-1,-1.3129E0), (6.9174E-1,-1.3744E0), (8.1460E-1,-1.4358E0), (8.9139E-1,-1.4358E0), (9.6818E-1,-1.4358E0), (1.0910E0,-1.3744E0), (1.2293E0,-1.2669E0), (1.3061E0,-1.1901E0), (1.3675E0,-1.1133E0), (1.4289E0,-1.0058E0), (1.4596E0,-9.4434E-1), (1.4750E0,-8.2147E-1), (1.5057E0,-7.1397E-1), (1.5057E0,-5.1432E-1), (1.5057E0,-4.0681E-1), (1.4903E0,-3.4538E-1), (1.4443E0,-4.0681E-1), (1.3675E0,-5.7575E-1), (1.3214E0,-7.2933E-1), (1.3061E0,-7.9076E-1), (1.3061E0,-7.2933E-1), (1.4136E0,-3.9145E-1), (1.4903E0,-2.3019E-1), (1.5518E0,-2.3787E-1), (1.6286E0,-2.8395E-1), (1.6746E0,-3.4538E-1), (1.7361E0,-4.3753E-1), (1.7668E0,-5.1432E-1), (1.7821E0,-5.9110E-1), (NaN,NaN), true]
B = Intersect(g, xAxis)
a = Surface(t, (g(t) * cos(s)), (g(t) * sin(s)), t, 0, x(B), s, 0, (2 * pi))