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 2018-12-15 05:50:43 -0500 received badge ● Good Answer (source) 2016-07-25 04:42:00 -0500 received badge ● Good Answer (source) 2016-05-25 01:24:27 -0500 received badge ● Nice Answer (source) 2015-03-20 04:11:28 -0500 received badge ● Good Answer (source) 2014-01-22 04:17:53 -0500 received badge ● Nice Answer (source) 2014-01-04 14:29:40 -0500 received badge ● Great Answer (source) 2014-01-03 16:00:17 -0500 received badge ● Good Answer (source) 2013-12-09 22:41:32 -0500 received badge ● Good Answer (source) 2013-07-16 19:15:54 -0500 received badge ● Nice Answer (source) 2013-07-08 00:40:21 -0500 received badge ● Nice Answer (source) 2013-04-05 00:56:51 -0500 received badge ● Enthusiast 2013-03-30 10:08:08 -0500 received badge ● Good Answer (source) 2013-03-13 02:07:42 -0500 commented question How to treat with logarithm numerically when it becomes negative? Have you tried: find_root(log(x*x-x),-2,0) -0.6180339887498988 find_root(log(x*x-x),-2,2) 1.6180339887498947 2013-02-24 07:59:25 -0500 commented answer 3d Complex function plot http://ask.sagemath.org/question/1767/coloring-surfaces-in-plot3d 2013-02-24 04:14:57 -0500 answered a question 3d Complex function plot My colouring is based on the z=f(x,y) value of the plotted function. Compare: sage: var('x y'); sage: cmsel = [colormaps['gnuplot2'](i) for i in sxrange(0,1,0.02)] sage: plot3d(lambda x,y:cos(sqrt(abs((x+I*y)*(x-I*y)))),(x,-2*pi,2*pi),(y,-2*pi,2*pi),adaptive=True,color=cmsel)  or: sage: cmsel = [colormaps['gnuplot2'](i) for i in sxrange(0.05,0.75,0.02)] sage: plot3d(lambda x,y:sin(x+I*y).imag(),(x,-2*pi,2*pi),(y,-2,2),adaptive=True,color=cmsel,mesh=True)  http://ask.sagemath.org/question/1405... 2013-02-23 23:59:51 -0500 answered a question 3d Complex function plot For example: sage: var('x y'); sage: cmsel = [colormaps['gnuplot2'](i) for i in sxrange(0,1,0.02)] sage: plot3d(lambda x,y:(sin(x+I*y)).imag_part(),(x,-3*pi,3*pi),(y,0,2),adaptive=True,color=cmsel)  2013-02-23 20:48:41 -0500 answered a question integral interpretation Sage gives you the correct answer. You can check it for example in wolframalpha. Ei  is the exponential integral (and not a product). To obtain a better formatted code you can copy-paste your code, mark it and use the 101... icon. 2013-02-21 04:33:00 -0500 received badge ● Nice Answer (source) 2013-02-15 23:16:04 -0500 answered a question How does one find solutions to a polynomial over a finite field? sage: E=EllipticCurve(GF(5),[0,1]);E Elliptic Curve defined by y^2 = x^3 + 1 over Finite Field of size 5 sage: pp=E.points() sage: [p.xy() for p in pp[1:]] [(0, 1), (0, 4), (2, 2), (2, 3), (4, 0)]  2013-02-13 17:17:18 -0500 commented answer Disabling y-axes in 2-D plot O.K. I did. 2013-02-13 08:48:47 -0500 commented answer Disabling y-axes in 2-D plot Try the edited version above 2013-02-13 05:18:39 -0500 answered a question Disabling y-axes in 2-D plot In matplotlib you can use for example the link http://www.shocksolution.com/2011/08/... In Sage you can use a workaround: p=plot(sin,ticks=[0.2,[]],thickness=3,zorder=20) p+=arrow((-1,0),(1,0),ticks=[0.2,[]],color='black',zorder=10) p.axes_color('white') p.show()  2013-02-12 04:16:09 -0500 received badge ● Nice Answer (source) 2013-02-11 23:17:18 -0500 answered a question Extracting a matrix from linear expressions maxima('coefmatrix([a-b,b-c,c-a],[a,b,c])').sage() [ 1 -1 0] [ 0 1 -1] [-1 0 1]  2013-02-05 08:21:27 -0500 answered a question Elliptic Curve functions don't seem to exist? Your commands are O.K.: sage: p=354990952970600489 sage: E = EllipticCurve(GF(p),[9326,1376127157]) sage: E Elliptic Curve defined by y^2 = x^3 + 9326*x + 1376127157 over Finite Field of size 354990952970600489  2013-01-22 17:10:56 -0500 commented answer Unable to evaluate integral of x*x/(exp(x)+1) Zeta is by definition the sum of a series, so this approach seems to be natural. I suspect that Mathematica uses a similar approach. As far as the speed is concerned: sage: timeit('numerical_integral(x^2/(exp(x)+1),0,oo)') 625 loops, best of 3: 1.36 ms per loop 2013-01-22 00:46:25 -0500 commented answer Unable to evaluate integral of x*x/(exp(x)+1) This method works for higher powers of x Wolfram alpha does not allow for x^n, n>4 2013-01-21 18:32:41 -0500 answered a question Unable to evaluate integral of x*x/(exp(x)+1) Maxima can not compute the limit but expanding into series and integrating term by term helps: sage: maxima('powerseries(x^2*exp(-x)/(exp(-x)+1),exp(-x),0)') x^2*%e^-x*'sum((-1)^i1*%e^-(i1*x),i1,0,inf) sage: var('k x'); sage: assume(k+1>0); sage: sum(integrate(x^2*exp(-x)*(-1)^k*exp(-(k*x)),x,0,oo),k,0,oo) 3/2*zeta(3)  2013-01-20 04:49:07 -0500 commented question simplify sinh expression sinh(log(1+sqrt(2))).n() 1.00000000000000 2013-01-18 21:45:05 -0500 answered a question Product of Elements in Group Use D(x)*D(y) instead of D(x*y): sage: D = SymmetricGroup(4) sage: H=D.subgroups() sage: A=Set(D(x)*D(y) for x in H for y in H) sage: print(A) {(1,4,3,2), (), (1,3,4), (2,4), (1,3,2,4), (1,2,3), (1,4,2,3), (1,2)(3,4)} sage: A=Set(D(x)*D(y) for x in H for y in H) sage: print(A) {(1,4), (1,3)(2,4), (1,3,4,2), (2,3), (3,4), (1,4,2,3), (), (2,3,4), (1,3,2,4), (1,4)(2,3), (1,4,3), (1,2,4), (1,2), (1,2)(3,4), (1,3,2), (1,2,4,3)}  2013-01-15 13:45:11 -0500 received badge ● Nice Answer (source) 2013-01-15 13:44:17 -0500 received badge ● Nice Answer (source) 2013-01-15 11:33:55 -0500 edited answer Matrices and mpmath Use mpmath operations to mpmath matrices M=mp.matrix([[2,0],[0,2]]) mp.inverse(M) matrix( [['0.5', '0.0'], ['0.0', '0.5']])  You can also control precision in Sage: sage: m=matrix(RealField(100),[[2,0],[0,2]]) sage: m^-1 [0.50000000000000000000000000000 0.00000000000000000000000000000] [0.00000000000000000000000000000 0.50000000000000000000000000000]