Are you looking for solutions to that equation?
Solve[Exp[x] == Cos[x] && -10 <= x <= 10, x, Reals]
(* Out[90]= {{x -> 0}, {x ->
Root[{-E^#1 + Cos[#1] &, -7.8535932799712482001}]}, {x ->
Root[{-E^#1 + Cos[#1] &, -4.7212927588476862166}]}, {x ->
Root[{-E^#1 + Cos[#1] &, -1.29269571937339838117}]}} *)
Or an iterative process that finds a solution from a starting point. For that one can use e.g. Newton iterations.
FixedPointList[{#[[1]] - f[#[[1]]]/f'[#[[1]]],
f[#[[1]]]} &, {-.7, f[-.2]}]
(* Out[112]= {{-0.7, -0.1613358247632598}, {-2.51705989723243, \
-0.268256883493079}, {-0.7474281702634069,
0.8919329283107287}, {-2.007816769456799, -0.2598565433504163}, \
{-1.285388510652165,
0.5575233413007432}, {-1.292717416706861, -0.005005670608255908}, \
{-1.2926957195615, 0.00001490725795189052}, {-1.292695719373398,
1.292351226034327*10^-10}, {-1.292695719373398, \
-5.551115123125783*10^-17}, {-1.292695719373398, \
-5.551115123125783*10^-17}} *)