Задачи
Angle
Angle
There are two points in the plane, so we can draw two segments between the original and each of them respectively. Calculate the angle between the two segments.
\includegraphics{https://static.e-olymp.com/content/49/49270e28ebc371c9e6e548fe5edf6353526f0ecb.jpg}
The angel should be a radian and less than (\textbf{3.1415926}…). Be careful, it's angle, not the cute angel.
\InputFile
The first line contains a single integer \textbf{T}, indicating the number of test cases. Each test case begins contains four integers \textbf{X_a}, \textbf{Y_a}, \textbf{X_b}, \textbf{Y_b} (\textbf{-10000} ≤ \textbf{X_a}, \textbf{X_b}, \textbf{Y_a}, \textbf{Y_b} ≤ \textbf{10000}), indicating the coordinates of the two points. You can assume both of them won't be the original point.
\OutputFile
For each case, output the angle rounded to three fractional digits.
Входные данные #1
2 0 1 1 0 1 2 2 1
Выходные данные #1
1.571 0.644