Question: highly anisotropic problems with phase field model (piecewise)

I am a student who is learning to use Maple to perform numerical analysis of phase field. There has been no solution to the problem of high anisotropy. The reference code is as follows

W :=piecewise(beta>=Pi/2+thetaM and beta<=Pi-thetaM, 1+eps*cos(4*beta), 
       beta>=Pi/2-thetaM and beta<=Pi/2+thetaM, (1+esp*cos(4*thetaM))/cos(thetaM)*cos(4*beta));

 

However, there is no problem at all when simply performing the following settings.

W := 1+ eps*cos(4*beta);

Please tell me how to write such a conditional maple statement. I have referenced many examples on the official website, but none of them succeeded. This includes writing the code in the following form.

W :=betta->piecewise(beta>=Pi/2+thetaM and beta<=Pi-thetaM, 1+eps*cos(4*beta), 
       beta>=Pi/2-thetaM and beta<=Pi/2+thetaM, (1+esp*cos(4*thetaM))/cos(thetaM)*cos(4*beta));

Remarks, beta is an angle, set as follows.

subs(beta=t_atan2(diff(pho(x,y),y), diff(pho(x,y),x))

 


 

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