lim (x→0) [(2x) / (1+x^2)]/sec x tan x+silim (x→0) [(2x) / (1+x^2)]/sec x tan x+sin x怎么算出lim (x→0)(x/sin x ) (cos x^2/1+cos x^2)(2/1+x^2)

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lim (x→0) [(2x) / (1+x^2)]/sec x tan x+silim (x→0) [(2x) / (1+x^2)]/sec x tan x+sin x怎么算出lim (x→0)(x/sin x ) (cos x^2/1+cos x^2)(2/1+x^2)
lim (x→0) [(2x) / (1+x^2)]/sec x tan x+si
lim (x→0) [(2x) / (1+x^2)]/sec x tan x+sin x怎么算出lim (x→0)(x/sin x ) (cos x^2/1+cos x^2)(2/1+x^2)

lim (x→0) [(2x) / (1+x^2)]/sec x tan x+silim (x→0) [(2x) / (1+x^2)]/sec x tan x+sin x怎么算出lim (x→0)(x/sin x ) (cos x^2/1+cos x^2)(2/1+x^2)
就化简一下就可以了
lim (x→0) [(2x) / (1+x^2)] / (sec x tan x+sin x)
=lim (x→0) [(2x) / (1+x^2)] / (sinx / cosx^2 +sin x)
=lim (x→0) 2/(1+x^2) *x *cosx^2 /(sinx + sinx *cosx^2)
=lim (x→0) x/sinx *cosx^2 / (1+cosx^2) *2/(1+x^2)