var('x,y')
(x, y)
E = implicit_plot( x^2 + 2*y^2 == 1, (x,-2,2), (y,-2, 2))
E
C = contour_plot(x*y, (x,-2,2), (y,-2,2), contours=[-2, -1, -1/(2*sqrt(2)), -0.2, 0, 0.2, 1/(2*sqrt(2)), 1, 2], fill='false')
C
C+E
Error in lines 1-1 Traceback (most recent call last): File "/cocalc/lib/python2.7/site-packages/smc_sagews/sage_server.py", line 1188, in execute flags=compile_flags) in namespace, locals File "", line 1, in <module> NameError: name 'C' is not defined