[CAS] ABS EXPAND new cmd

[compsystems]

solve((r^2) = ((r*sin(x)-4)^2),r); returns

{ (4/(sin(x)-1)), (4/(sin(x)+1)) }

Early transcendentals by Dennis G. Zill and others ... book show

r^2 = (r*sin(x)-4)^2

√(r^2) = √((r*sin(x)-4)^2)

r = +(r*sin(x)-4) or r = -(r*sin(x)-4)

r-r*sin(x) = -4 or r+r*sin(x) = -4

r*(1-sin(x)) = -4 or r*(1+sin(x)) = -4

r = -4/(1-sin(x)) or r = -4/(1+sin(x))

You can see the importance ABS EXPAND command, which is available in the CLASPAD400 And I wish please, that Bernard can also include him in the xCAS.