Hello Professor,

I keep having problems using sage. When I get to the part where I have to plot, I get the following message and the plot comes out completely blank:

__main__:4: DeprecationWarning: Substitution using function-call syntax and unnamed arguments is deprecated and will be removed from a future release of Sage; you can use named arguments instead, like EXPR(x=…, y=…) See http://trac.sagemath.org/5930 for details.

I am having the same issue with both, problem 14 and 18. However I am able to plot the vector fields and do everything else. I attached a copy of my work so you can take a look at it and tell me what am I doing wrong. Thank You.

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The problem is that following command:

var(‘x y’)

implicit_plot(-1/2/y(x)^2 == sqrt(x^2 + 1) – 3/2,(x,-5,5),(y,-5,5))

Solutions:

(1) Evaluate the command for a second time.

(2) Instead of y(x) use just y. I.e.

implicit_plot(-1/2/y^2 == sqrt(x^2 + 1) – 3/2,(x,-5,5),(y,-5,5))

Also, keep in mind that depending on the problem, you may have to adjust your “window”. In the above case x is between -5 and 5 and the same is true for y. Adjust the values accordingly.

Does this help?

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