2017-12-19 21:34:57 +0200 received badge ● Notable Question (source) 2017-12-19 21:34:57 +0200 received badge ● Famous Question (source) 2015-11-16 12:48:34 +0200 received badge ● Popular Question (source) 2015-04-13 21:03:45 +0200 received badge ● Teacher (source) 2015-04-11 16:29:03 +0200 received badge ● Supporter (source) 2015-04-11 13:41:34 +0200 received badge ● Student (source) 2015-04-11 02:30:20 +0200 commented answer Why is sage giving me wrong answers? There is a similar question in this thread http://ask.sagemath.org/question/1006... 2015-04-11 02:08:41 +0200 commented answer Why is sage giving me wrong answers? Can be written this way too var('t,v,a,b', domain="complex"); v=sqrt(-3); a=(-1+v)/2; b=(-1-v)/2; t=a*b; t.real(); t.imag();  or this way var('t,v', domain="complex"); v=sqrt(-3); t=((-1+v)/2)*((-1-v)/2); t.expand().factor();  2015-04-11 01:46:27 +0200 received badge ● Editor (source) 2015-04-11 01:37:57 +0200 commented answer Why is sage giving me wrong answers? OOOPs it doesn't work i=CC(-3); j=CC(-1); k=CC(2); t = ((j + sqrt(i))/k)*((j - sqrt(i))/k); t.real(); t.imag();  The error moved into he imaginary part (approx 0.5 E-16). I must edit the answer ..... 2015-04-11 01:34:50 +0200 commented answer Why is sage giving me wrong answers? Sage complex numbers are based on floating points, 1+2i is implemented as 1.00000000 + 2.00000000000 * i. 2015-04-11 01:00:20 +0200 answered a question Why is sage giving me wrong answers? Default complex numbers use double precision floating points and their rounding errors (which can't be avoided). Use variable from the right field and arithmetic specific to complex numbers var('t,v,a,b', domain="complex") v=sqrt(-3); a=(-1+v)/2; b=conjugate(a); t = a*b; v; a; b; t.real(); t.imag();  displays sqrt(-3) 1/2*sqrt(-3) - 1/2 1/2*conjugate(sqrt(-3)) - 1/2 1 0  2015-04-10 23:38:04 +0200 asked a question Compute the determinant of a symbolic 5x5 matrix why does the following script fail to compute the determinant of a 5x5 matrix (same problem appears with larger similar matrices 6x6 and 7x7 matrix too) ? version(); var ('a,b,c,d,e,f,g,h'); A4 = matrix(SR,4,4,[a,b,c,d,a,a,b,c,a,a,a,b,h,a,a,a]); A5 = matrix(SR,5,5,[a,b,c,d,e,a,a,b,c,d,a,a,a,b,c,a,a,a,a,b,h,a,a,a,a]); A4; A4.determinant().expand().factor(); A5; A5.determinant(); A5.determinant().expand().factor();  a spurious "_e" appears in the determinant 'Sage Version 6.5, Release Date: 2015-02-17' (a, b, c, d, e, f, g, h) [a b c d] [a a b c] [a a a b] [h a a a] a^4 - 3*a^3*b + 3*a^2*b^2 - 2*a^2*b*c + a^2*c^2 + a^3*d - a^2*b*d - b^3*h + 2*a*b*c*h - a*c^2*h - a^2*d*h + a*b*d*h [a b c d e] [a a b c d] [a a a b c] [a a a a b] [h a a a a] _e*a^4 + a^5 - 2*_e*a^3*b - 4*a^4*b + _e*a^2*b^2 + 6*a^3*b^2 - 4*a^2*b^3 + 3*a^2*b^2*c - a^3*c^2 - 2*a^2*b*c^2 + a^2*c^3 - 2*a^3*b*d + 2*a^2*b^2*d + 2*a^3*c*d - 2*a^2*b*c*d - _e*a^3*h + 2*_e*a^2*b*h - _e*a*b^2*h + b^4*h - 3*a*b^2*c*h + a^2*c^2*h + 2*a*b*c^2*h - a*c^3*h + 2*a^2*b*d*h - 2*a*b^2*d*h - 2*a^2*c*d*h + 2*a*b*c*d*h Error in lines 13-19 Traceback (most recent call last): File "/projects/cbc78de9-848d-4653-bf96-aa8a68749e86/.sagemathcloud/sage_server.py", line 879, in execute exec compile(block+'\n', '', 'single') in namespace, locals File "", line 1, in File "sage/symbolic/expression.pyx", line 9266, in sage.symbolic.expression.Expression.factor (build/cythonized/sage/symbolic/expression.cpp:45045) f = self.polynomial(QQ) File "sage/symbolic/expression.pyx", line 5716, in sage.symbolic.expression.Expression.polynomial (build/cythonized/sage/symbolic/expression.cpp:31627) return polynomial(self, base_ring=base_ring, ring=ring) File "/usr/local/sage/sage-6.5/local/lib/python2.7/site-packages/sage/symbolic/expression_conversions.py", line 1163, in polynomial converter = PolynomialConverter(ex, base_ring=base_ring, ring=ring) File "/usr/local/sage/sage-6.5/local/lib/python2.7/site-packages/sage/symbolic/expression_conversions.py", line 999, in __init__ self.ring = PolynomialRing(self.base_ring, names=vars) File "/usr/local/sage/sage-6.5/local/lib/python2.7/site-packages/sage/rings/polynomial/polynomial_ring_constructor.py", line 477, in PolynomialRing R = _multi_variate ...