## dharr

Dr. David Harrington

## 5931 Reputation

19 years, 272 days
University of Victoria
Professor or university staff

## Social Networks and Content at Maplesoft.com

I am a professor of chemistry at the University of Victoria, BC, Canada, where my research areas are electrochemistry and surface science. I have been a user of Maple since about 1990.

## de Morgan's laws...

I didn't look in the programming guide, but to show de Morgan's laws I would just do: with(Logic): Equivalent(¬(a &and b), (¬ a) &or (¬ b)); Equivalent(¬(a &or b), (¬ a) &and (¬ b)); Since both are true this is a proof. Cheers, David.

## where would you plot it?...

note that x=10 (log(x)=1) is plotted one unit of length to the left of x=100 (log(x)=2). So moving left one unit each time, we plot x values of 100 10 1 0.1 0.01 1e-3 1e-4 1e-5 1e-6 Since log(0)= -infinity, very far left we get very small positive values, but we never get to negative x values.

## where would you plot it?...

note that x=10 (log(x)=1) is plotted one unit of length to the left of x=100 (log(x)=2). So moving left one unit each time, we plot x values of 100 10 1 0.1 0.01 1e-3 1e-4 1e-5 1e-6 Since log(0)= -infinity, very far left we get very small positive values, but we never get to negative x values.

## I like it...

This perfectly represents the Maple learning curve, and is very much the way I go about things, i.e., you eventually get it, and then contract it down. In simple cases like this, where I know where I am headed and just want to check it, I simplify the difference of my starting expression and my guess and check for zero; in your case that would be: simplify((tan(a)+tan(b))/(1-tan(a)*tan(b))-tan(a+b)); But it doesn't work! A quick fiddle and it does simplify(expand(tan(a)+tan(b))/(1-tan(a)*tan(b))-tan(a+b))); Cheers, David.

## nested diffs...

Glad it worked for you. Just a tip: diff(y(x), x, x, x, x); is simpler as diff(y(x), x, x, x, x); which can be further abbreviated as diff(y(x), x\$4);

## nested diffs...

Glad it worked for you. Just a tip: diff(y(x), x, x, x, x); is simpler as diff(y(x), x, x, x, x); which can be further abbreviated as diff(y(x), x\$4);

## ordering of plots...

That's interesting, and very mysterious. Do you get it OK with my example? I am using Maple 10 under Windows. The only other thing I can think of would be that using a list might force the order, and I was just lucky skipping it. display([points, curve]); display([curve,points]);

## ordering of plots...

That's interesting, and very mysterious. Do you get it OK with my example? I am using Maple 10 under Windows. The only other thing I can think of would be that using a list might force the order, and I was just lucky skipping it. display([points, curve]); display([curve,points]);

## thanks...

Thanks, this works. I look forward to Maple 11 then.

## thanks...

Thanks, this works. I look forward to Maple 11 then.

## Thanks for the help on help...

Thanks for pointing me there, I would never have found. I can now do what I want to. BTW, you can save at least simple *.mw files as help pages with makehelp (which just reads the lines and calls INTERFACE_HELP), but not sure which features you might lose.

## Thanks for the help on help...

Thanks for pointing me there, I would never have found. I can now do what I want to. BTW, you can save at least simple *.mw files as help pages with makehelp (which just reads the lines and calls INTERFACE_HELP), but not sure which features you might lose.

## It is a problem in a program...

I agree about the difficulty and annoyance in a long code of finding such problems. But qualified responses could quickly get complicated. Consider solve(a*x^2+b*x+c,x); This needs a qualification that a<>0, which is simple enough. But should it also be mentioned that there is one answer, not two, if b^2=4*a*c? And that if a=0, then the solution is -c/b unless b=0, in which case the equation doesn't have x in it any more ... Cheers, David.
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