= lim & ltx→0 & gt; ln( 1+x? )/[( 1/cosx)-cosx]
= lim & ltx→0 & gt; cosx ln( 1+x? )/( 1-cos? x)
= lim & ltx→0 & gt; ln( 1+x? )/sin? x
= lim & ltx→0 & gt; 【2x/( 1+x? )]/(2sinxcosx)
= lim & ltx→0 & gt; 【2x/( 1+x? )]/(sin2x)
= lim & ltx→0 & gt; 2x/(sin2x)
= 1
(1) How does the natural gas ladder charge work?
Cities are different, one more step is expensive, and two more steps are expensive.