result of atan is never more precise than double

3 results were exact to double the precision

20 largest ulp errors (stored in a double)
   0.51270 ulp for atan(-3.1008624240000038) = -1.2588354688269643)
   0.51179 ulp for atan(-0.40517564640000125) = -0.38496016305180936)
   0.51163 ulp for atan(0.87853474179999869) = 0.72082847382491344)
   0.51111 ulp for atan(-7.3702754219999944) = -1.4359396930025512)
   0.50960 ulp for atan(-0.73224416179999918) = -0.63204019076294804)
   0.50635 ulp for atan(0.83391883199999639) = 0.69508371690996795)
   0.50631 ulp for atan(0.11815269319999985) = 0.11760744678260585)
   0.50531 ulp for atan(0.19658675319999855) = 0.19411144790195325)
   0.50437 ulp for atan(-7.7915039100000225) = -1.4431492329333908)
   0.50424 ulp for atan(-1.7985095260000104) = -1.0633460729613728)
   0.50375 ulp for atan(8.1257804540000826) = 1.4483469141269474)
   0.50361 ulp for atan(-2.3905798040000064) = -1.1746070116926659)
   0.50356 ulp for atan(-6.8105881539999809) = -1.4250078633418839)
   0.50353 ulp for atan(-0.61884908699999752) = -0.55416395454212508)
   0.50306 ulp for atan(-0.26083472800000257) = -0.25514977284240559)
   0.50297 ulp for atan(-4.3680301419999985) = -1.3457385739935601)
   0.50284 ulp for atan(-7.7915039100002144) = -1.4431492329333939)
   0.50284 ulp for atan(-0.75809214000000447) = -0.64865999416578479)
   0.50261 ulp for atan(-0.25078269240000106) = -0.24571517902533635)
   0.50245 ulp for atan(4.9471405239999688) = 1.3713468342256021)

<tr><td align=left><a href=atan.res>atan</a></td><td align=right>870</td><td align=right>0.51270</td><td>-3.1008624240000038</td><td>-1.2588354688269643</td></tr>