in the Cartesian coordinate system, how to calculate the rotation angle of two lines connected by two points and 0 in Cartesian coordinate system, that is, how to realize this method
, it returns a negative number counterclockwise, that is,-180 degreesgetAngle (x1, y1, x2, y2, x3, y3) {
}
getAngle(0,0,0,-1,0,1)
// -180
getAngle(0,0,0,-1,-1,-1)
// 45$$ Arccos (\ frac {(x_2-x_1) * (x_3-x_1) + (y_2-y_1) * (y_3-y_1)} {\ sqrt {(x_2-x_1) ^ 2 + (y_2-y_1) ^ 2} *\ sqrt {(x_3-x_1) ^ 2 + (y_3-y_1) ^ 2}}) $
now that you know the coordinates of the two points,
yes=>180
no=>
=>
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