1.用洛必达法则求下列极限:-|||-(1) lim _(xarrow 0)dfrac (ln (1+x))(x)-|||-(4) lim _(xarrow pi )dfrac (sin 3x)(tan 5x) =-|||-(7) lim _(xarrow 0)dfrac (ln tan 7x)(ln tan 2x) ;-|||-(10) lim _(xarrow 0)dfrac (ln (1+{x)^2)}(sec x-cos x) ;-|||-(13) lim _(xarrow 1)(dfrac (2)({x)^2-1}-dfrac (1)(x-1)) ;-|||-(16) lim _(xarrow {0)^+}((dfrac {1)(x))}^tan x --|||-(2) lim _(xarrow 0)dfrac ({e)^x-(e)^-x}(sin x) ;-|||-(5) lim _(xarrow dfrac {pi )(2)}dfrac (ln sin x)({(pi -2x))^2} :-|||-(8) lim _(xarrow dfrac {pi )(2)}dfrac (tan x)(tan 3x) ;-|||-(11) lim _(xarrow 0)xcot 2x ;-|||-(14) lim _(xarrow infty )((1+dfrac {a)(x))}^x-|||-(3) lim _(xarrow a)dfrac (sin x-sin a)(x-a) ;-|||-(6) lim _(xarrow a)dfrac ({x)^m-(a)^m}({x)^n-(a)^n} ;-|||-(9) lim _(xarrow +infty )dfrac (ln (1+dfrac {1)(x))}(arctan x) ;-|||-(12) lim _(xarrow 0)(x)^2(e)^dfrac (1{{x)^2}} ;-|||-(15) lim _(xarrow {0)^+}(x)^sin x ;