``````````1`-`tan`3x`````````tan`45°-`tan 3x``````````````````
````y=--------------- = -------------------------```````````````
``````````1`+`tan`3x```````1`+`tan`45°×tan 3x````````````
````````````````````````````````````````````
`````=tan(45°-3x) (差角公式)`````````````````````
````````````````````````````````````````````
````∴ω`=`3``````````````````````````````````````
````````````````````````````````````````````
````````````π```π```````````````````````````````
````∴T`=`-`=`-`````````````````````````````````
````````````ω```3```````````````````````````````