Recent content by ilya.s

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    Undergrad How to get formula for focus and directrix

    Hello everyone, this is an amazing forum! :) I have a question: I have seen the formulas for focus/directrix of a parabola, but I cannot trust something unless I know how to get there. How do I get the formulas of focus and directrix? I got to an equation (X - Xf)^2 + (Y - Yf)^2 = (Y -...