I have defined four functions

```
fA(x_,y_):=Sqrt(x^2+(y+2)^2)
fAB(x_,y_):=Sqrt((x-3)^2+(y+1)^2)*Boole((y>=(1/2-(1/2)*x)))+(Sqrt(5)+Sqrt((x-1)^2+(y)^2))*Boole((y<(1/2-(1/2)*x)))
fABC(x_,y_):=Sqrt((x-3)^2+(y-3)^2)*Boole((y>=x))+(2*Sqrt(2)+Sqrt((x-1)^2+(y-1)^2))*Boole((y
```(1-(3/2)*x)))

Before defining the room, I used Solve and it worked as expected.

However, after defining the room, Solve stopped working, even for functions it previously worked for.

```
Solve(fA(x,y)==fABC(x,y),y)
```

Now it gives the error "Solve: Undefined is not a valid variable" and returns

`Solve(Undefined,Undefined)`

The problem seems to have something to do with the variable `y`

, since Solve still works well with other variables.

Does anyone know what could have gone wrong? Sorry if an equivalent question has already been asked. I couldn't find one.