if we have the following system:
((tanx)/(tany))=a
x±y=α
we have the general candition:
−1≤(((a−1)/(a+1)))sinα≤1
if you apply the general candition by
the following system it does not give
us the reality, despite this system have
the solution.
((tanx)/(tany))=−3
x−y=(π/2)
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