Question

lim -> 0 sin(2x) /(x*cos(x) )

help

Answer 1

sin (2x) can be written like:sin (2x) = 2sin(x)cos(x)
substituting this expresion in the original one:sin(2x) /(x*cos(x) =2sin(x)cos(x)/x*cos(x)=2sinx/x
taking limits, and noticing that lim as x->0 of sinx/x=1:lim 2sinx/x=2*1=2x->0