(with-test-prefix "angle"
  (define pi 3.14159265358979323846)
  (define (almost= x y)
    (> 0.01 (magnitude (- x y))))
  
  (pass-if "inum +ve"   (=        0 (angle 1)))
  (pass-if "inum -ve"   (almost= pi (angle -1)))

  (pass-if "bignum +ve" (=        0 (angle (1+ fixnum-max))))
  (pass-if "bignum -ve" (almost= pi (angle (1- fixnum-min))))

  (pass-if "flonum +ve" (=        0 (angle 1.5)))
  (pass-if "flonum -ve" (almost= pi (angle -1.5))))