atan -- compute the arctangent of a number

• Usage:

  atan x

  atan I

• Inputs:
  • x, a real number
  • I, a real interval
• Outputs:
  • a real number, the arctangent (in radians) of x
  • a real interval, an interval containing the arctangents of the points of I

i1 : atan 1

o1 = .7853981633974483

o1 : RR (of precision 53)

i2 : abs atan 1 == pi/4

o2 = true