JS中求反正切Math.atan()返回值的问题

Question

查  Math.atan(x) 知，x可以为任意数，Math.atan(x)返回值在（-π/2,π/2）之间，但总是不对，为验证，写直接打印语句如下： $j("#console3").append(
"atan(-999999999999999999)="+Math.atan(-999999999999999999)*180+"</br>"+
"atan(-999)="+Math.atan(-999)*180+"</br>"+
"atan(-9)="+Math.atan(-9)*180+"</br>"+
"atan(-1)="+Math.atan(-1)*180+"</br>"+
"atan(-0.5)="+Math.atan(-0.5)*180+"</br>"+
"atan(-0.1)="+Math.atan(-0.1)*180+"</br>"+
"atan(-0.01)="+Math.atan(-0.01)*180+"</br>");结果：
atan(-999999999999999999)=-282.7433388230814
atan(-999)=-282.5631587030815
atan(-9)=-262.8250390117802
atan(-1)=-141.3716694115407
atan(-0.5)=-83.4565696201451
atan(-0.1)=-17.940357448409166
atan(-0.01)=-1.7999400035997428
怎么解释！？

Answer 1

以为做一个图形，无法避免使用  Math.atan()  函数，但却出现这样的情况，实在纠结！

Answer 2

document.write(
"atan(-999999999999999999)="+Math.atan(-999999999999999999)*180/Math.PI+"</br>"+
"atan(-999)="+Math.atan(-999)*180/Math.PI+"</br>"+
"atan(-9)="+Math.atan(-9)*180/Math.PI+"</br>"+
"atan(-1)="+Math.atan(-1)*180/Math.PI+"</br>"+
"atan(-0.5)="+Math.atan(-0.5)*180/Math.PI+"</br>"+
"atan(-0.1)="+Math.atan(-0.1)*180/Math.PI+"</br>"+
"atan(-0.01)="+Math.atan(-0.01)*180/Math.PI+"</br>")atan(-999999999999999999)=-90
atan(-999)=-89.94264688651026
atan(-9)=-83.6598082540901
atan(-1)=-45
atan(-0.5)=-26.56505117707799
atan(-0.1)=-5.710593137499643
atan(-0.01)=-0.5729386976834859

Answer 3

完整如下：
$j("#console3").append(
"atan(-999999999999999999)="+Math.atan(-999999999999999999)*180+"</br>"+
"atan(-999)="+Math.atan(-999)*180+"</br>"+"atan(-9)="+Math.atan(-9)*180+"</br>"+
"atan(-1)="+Math.atan(-1)*180+"</br>"+"atan(-0.5)="+Math.atan(-0.5)*180+"</br>"+
"atan(-0.1)="+Math.atan(-0.1)*180+"</br>"+"atan(-0.01)="+Math.atan(-0.01)*180+"</br>"+
"atan(0)="+Math.atan(0)*180+"</br>"+"atan(0.01)="+Math.atan(0.01)*180+"</br>"+
"atan(0.1)="+Math.atan(0.1)*180+"</br>"+"atan(0.5)="+Math.atan(0.5)*180+"</br>"+
"atan(1)="+Math.atan(1)*180+"atan(9)="+Math.atan(9)*180+"</br>"+
"atan(999)="+Math.atan(999)*180+"</br>"+
"atan(999999999999999999)="+Math.atan(999999999999999999)*180+"</br>");结果：
atan(-999999999999999999)=-282.7433388230814
atan(-999)=-282.5631587030815
atan(-9)=-262.8250390117802
atan(-1)=-141.3716694115407
atan(-0.5)=-83.4565696201451
atan(-0.1)=-17.940357448409166
atan(-0.01)=-1.7999400035997428
atan(0)=0
atan(0.01)=1.7999400035997428
atan(0.1)=17.940357448409166
atan(0.5)=83.4565696201451
atan(1)=141.3716694115407atan(9)=262.8250390117802
atan(999)=282.5631587030815
atan(999999999999999999)=282.7433388230814范围在（-282.7433388230814，282.7433388230814）之间

Answer 4

 我没发现有什么不对呀 Math.atan(x)返回值都在（-π/2,π/2）之间 你乘180以后当然不在（-π/2,π/2）之间了