Items tagged with csgn

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Hi,

I was wondering why when I want to equate

arctan(0, z)

Maple returns

arctan(0, z)

I know that the maple arctan(x,y) (or atan2) plots from Pi/..-Pi/2, but at x = 0, depending on the sign of y, it should either return Pi/2 or -Pi/2. but the equation returned wouldnt do that, It will plot only from Pi/2 to 0. see below.

plot(arctan(0,z), z = -1..1)

first, why does maple evaluate it to that particular expression of csgn?
second, how to get a "correct" result?

Hi All,

 

I have o problem with simplify. A variable cp1r has been assumed to be positive. Why simplify still has csgn(cp1r) for it? Here is my code:

tmp := subs(cp1t(t)=cp1r, cp2t(t)=cp2r, Ca[2]);
1 / 2 2
----------- |-cp2r sin(x[1]) sin(x[7]) cp1r
2 2 |
cp1r cp2r |
\

2
+ 2 cp2r sin(x[1]) cos(x[1]) cos(x[7]) sin(x[7]) cp1r +

1 / 2 2 /
-------------- \cp2r cos(x[1]) cos(x[7]) sin(x[7]) \
(1/2)
/ 2\
2 \cp1r /
2 \\\
-2 cos(x[1]) cos(x[7]) sin(x[1]) + 2 sin(x[1]) cos(x[1])//|
|
|
/
assume(cp1r > 0, cp2r > 0);
simplify(tmp);
1 / / 3 3
---------- \sin(x[1]) sin(x[7]) \-cos(x[1]) cos(x[7])
2
cp1r cp1r

+ 2 cos(x[1]) cos(x[7]) cp1r csgn(cp1r) cp1r

2 3 \ \

- cp1r csgn(cp1r) cp1r + cos(x[1]) cos(x[7])/ csgn(cp1r)/

 

should csgn(cp1r) be simplified to 1 already? What is wrong with my script?

 

Thanks 

Everett

Hi,

I am trying to simplify the expression s as given below. (I am not sure why it comes up with all the vector caclulus notation in it but it should display okay when you enter it)

Because of the presence of the exponential imaginary fucntions I thought evalc might be useful but when I use it I get a huge expression with csgn appearing in it. To my knowledge csgn appears when assumptions are not correctly specified - is this so? I can't see any assumption...

Hi guys please help me with the following.

 

When I evaluate the integral below

int(1/8*2^(1/2)*exp(-1/2*x^2/sigma^2)/(Pi^(5/2)*sigma)+1/8*2^(1/2)*exp(-1/2*x^2/sigma^2)*Q*exp(I*k*x)*exp(I*k*theta)/(Pi^(3/2)*sigma)+1/8*2^(1/2)*exp(-1/2*x^2/sigma^2)*Q/(Pi^(3/2)*sigma*exp(I*k*x)*exp(I*k*theta)), x = (-infinity .. infinity));    --------(1)

 

I get an expression with things like 

csgn(conjugate(sigma)) and 

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