How to Simplify an symbolic expression
1 回表示 (過去 30 日間)
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Hi all, I want to simplify this equation
a= 2 atan((-2+Sqrt(4-gama^2 *l^2* M^2-4* gama *l* M^2 *tan(gama/2)+4* tan(gama/2)^2-4 *M^2 *tan(gama/2)^2))/(gama* l* M+2* tan(gama/2)+2* M* tan(gama/2)))
into this form
a= (gama/2)-asin(((gama*l*M)/2)*cos(gama/2)+M*sin(gama/2))
Can anyone help?
7 件のコメント
Torsten
2017 年 4 月 20 日
Or maybe this can help:
https://de.mathworks.com/help/symbolic/isequaln.html
Best wishes
Torsten.
回答 (2 件)
Andrew Newell
2017 年 4 月 21 日
If I define
a= 2*atan((-2+sqrt(4-gama^2 *l^2* M^2-4* gama *l* M^2 *tan(gama/2)+4* tan(gama/2)^2-4 *M^2 *tan(gama/2)^2))/(gama* l* M+2* tan(gama/2)+2* M* tan(gama/2)));
b = (gama/2)-asin(((gama*l*M)/2)*cos(gama/2)+M*sin(gama/2));
and substitute pi for gama,
subs(a,gama,pi)
subs(b,gama,pi)
I get a==NaN and b==pi/2 - asin(M). So they are not the same. I find that applying simplify to a does not change it significantly.
5 件のコメント
Torsten
2017 年 4 月 21 日
I still don't understand why you try to transform the first expression into the second if - as you write - you are sure that both expressions yield the same values for a (at least in cases where both expressions are real-valued).
Best wishes
Torsten.
Walter Roberson
2017 年 4 月 21 日
I randomly substituted M=2, l=3. With those two values, the two expressions are not equal. One of the two goes complex from about gama = pi to gama = 17*pi/16 . From 17*pi/16 to roughly 48*Pi/41 the difference between the two is real valued . After that the difference has a real component of 2*pi and an increasing imaginary component.
8 件のコメント
Andrew Newell
2017 年 4 月 23 日
To summarize what Walter and I are saying, the two expressions are clearly not always equal, and the conditions under which they are equal are hard to pin down. Perhaps you should look more closely at how they did it in the article. Not that published work is always 100% correct.
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