(6)
lim(x->α) (sinx- sinα) /(x-α) (0/0)
=lim(x->α) cosx
=cosα
(7)
â(x^2+x) - â(x^2-x)
=[â(x^2+x) - â(x^2-x)] . [â(x^2+x) + â(x^2-x)]/[â(x^2+x) + â(x^2-x)]
= 2x/[â(x^2+x) + â(x^2-x)]
lim(x->â) [â(x^2+x) - â(x^2-x) ]
=lim(x->â) 2x/[â(x^2+x) + â(x^2-x)]
=lim(x->â) 2/[â(1+1/x) + â(1-1/x)]
=2/(1+1)
=1
(8)
lim(x->0) [ ( 1- (1/2)x^2)^(2/3) -1 ]/[xln(1+x) ]
=lim(x->0) - (1/3)x^2 /x^2
=-1/3
x->0
( 1- (1/2)x^2)^(2/3) ~ 1 - (2/3)(1/2)x^2 = 1- (1/3)x^2
( 1- (1/2)x^2)^(2/3) -1 ~ - (1/3)x^2
ln(1+x) ~ x
xln(1+x) ~ x^2
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