Two lines: a 1 x + b 1 y + c 1 = 0 and...
Two lines: and are given. I know that the equation of its bisectors is But I intend to find which one is the obtuse angle bisector and which one is the acute angle bisector. I want to find a general formula Assuming both are of same sign, I know if and if we take the positive sign we get the obtuse angle bisector and vice versa. But I want to prove it using general equation of line, I tried to find the angle between bisector and original line i.e. and then if it is greater than one it will be of obtuse angle but calculations are tough if we use general equation of line. May anyone give a simple proof of the following statement: "Assuming both are of same sign IF then if we take positive sign we get the obtuse angle bisector".