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How do I get rid of I/Complex ? (Thomas Calculus 8.8.5)

Posted on 2008-09-07 19:21 By KewlEugene (Maple Rating 1 20)
Categories:

 How do I get rid of the 'I" in the 1st limit shown ? (The answer should be 3/2). The 2nd limit looks fine.

‹ What command to find intersection of two functions how to determine temp. distribution in maple ›

use RealDomain

Comment on 2008-09-07 19:58 from jakubi (Maple Rating 4 911)

It can be done this way:

use RealDomain in limit(Int(x^(-1/3),x=-1..b),b=0,left) end;
                                 -3/2

YOU THE MAN ! i now

Comment on 2008-09-07 20:06 from KewlEugene (Maple Rating 1 20)

YOU THE MAN !

i now have

with(RealDomain):

at the start of my worksheet.

thanks.

Doug Meade's picture

use and with

Comment on 2008-09-09 10:23 from Doug Meade (Maple Rating 4 715)

You may not want to load RealDomain at the beginning of your worksheet.

There are significant parts of Maple that depend on being able to work in the complex domain. I prefer to be more surgical in my use of RealDomain. As illustrated in the earlier response to your post, the

use RealDomain in ... end use

style is my preferred usage.

The use statement is relatively new to Maple and many users have yet to discover it or to adapt their usage to include it. I hope questions like yours can help to spread the word.

Doug

---------------------------------------------------------------------
Douglas B. Meade  <><
Math, USC, Columbia, SC 29208  E-mail: mailto:meade@math.sc.edu       
Phone:  (803) 777-6183         URL:    http://www.math.sc.ed

  understood. now can i ask

Comment on 2008-09-09 17:57 from KewlEugene (Maple Rating 1 20)

 

understood.

now can i ask you,  how do i get rid of the "csgn" in the below ? it only happens with 1/3 of the variations of this exercise. thanks.

acer's picture

sorry

Comment on 2008-09-09 19:10 from acer (Maple Rating 4 1359)

Sorry, I answered this out of order.

acer

acer's picture

assumption on t

Comment on 2008-09-09 19:06 from acer (Maple Rating 4 1359)

Try this,

> with(student): with(RealDomain):

> F := int(sqrt(u),u=0..t^10);
                                            5   15
                             F := 2/3 csgn(t ) t

> simplify(F) assuming t::real;
                                           15
                                  2/3 | t |

> df := diff(F,t);
                                     5   15            5   14
                  df := 2/3 csgn(1, t ) t   + 10 csgn(t ) t
 
> evalc(df);
                                           5  14
                               10 signum(t)  t

> simplify(%) assuming t::real;
                                         13
                                 10 | t |   t

Maple also came up with the following, though it took much longer than it ought to have done.

> F := int(sqrt(u),u=0..t^10) assuming t::real;
                                      15
                            F := 2/3 t   signum(t)

I originally gave a flippant answer to this question. But, under the RealDomain environment, the assumption that t is real doesn't seem strained. Also, Maple didn't seem able to simplify(df) nicely and immediately under the assumption that t was real. Hence I made intermediate use of evalc. Having to use `assuming` and evalc underneath RealDomain doesn't look so good.

acer

that did it man. thanks.

Comment on 2008-09-09 21:17 from KewlEugene (Maple Rating 1 20)

that did it man. thanks.

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