Question #78c16

1 Answer
May 23, 2017

#lim_(x->0) (sinx)^x = 1#

Explanation:

Given:

#f(x) = (sinx)^x#

Consider:

#g(x) = ln(f(x)) = ln ((sinx)^x) = x ln sinx#

If we consider the limit:

#lim_(x->0) x ln sinx#

it is in the indeterminate form #0*oo# but we can reduce it to the form #oo/oo# by writing it as:

#g(x) = ln sinx /(1/x)#

and then apply l'Hospital's rule:

#lim_(x->0) g(x) = lim_(x->0) (d/dx( ln sinx))/(d/dx (1/x)) = lim_(x->0) -x^2 cosx/sinx #

As we know that: #lim_(x->0) sinx/x = 1#

we have:

#lim_(x->0) g(x) = lim_(x->0) (-x)(x/sinx) cosx = 0 xx 1 xx 1 = 0 #

Now, as:

#f(x) = e^g(x)#

and as #e^x# is continuous in all #RR# we have:

#lim_(x->0) f(x) = lim_(x->0) e^g(x) = e^(lim_(x->0) g(x)) = e^0 = 1#