# atan2 -- compute an angle of a certain triangle

## Synopsis

• Usage:
atan2(y,x)
atan2(y,I)
atan2(J,x)
atan2(J,I)
• Inputs:
• y,
• x,
• J,
• I,
• Outputs:
• , the angle (in radians) formed with the x-axis by the ray from the origin to the point (x,y)
• , an interval containing the angles (in radians) formed with the x-axis by the rays from the origin to the points of (I,y),(x,J),(I,J)

## Description

 i1 : atan2(1,0) o1 = 1.5707963267949 o1 : RR (of precision 53) i2 : atan2(0,1) o2 = 0 o2 : RR (of precision 53) i3 : atan2(-1,-1) o3 = -2.35619449019234 o3 : RR (of precision 53)