Question

can you tell me whats the difference between cosx and coshx ?

Answer 1

cosh is the hyperbolic cosine function

Answer 2

In comparing the two, I think of cos(x) as being based and defined in terms of the unit circle whereas cosh(x) is based and defined on the unit hyperbola.

Answer 3

if you are doing a chapter of limits then h is defined as tending to zero so cos hx will be tending to cos 0 i.e. tending 1