What is the domain and range of #y= 4 cos x#?

1 Answer

Domain: #x in RR#
Range: #-4geyge4#

Explanation:

The domain is the list of all allowable #x# values - that is to say - it results in #y# values that are defined.

With the function #cos#, it's a sinusoidal graph that cycles around the #x#-axis:

graph{4cosx}

and so the domain is all reals, or #x in RR#

The range is the list of all the values generated from the domain.

In this case, the resulting #y# values cycle between 4 and #-4#, and so the range is #-4geyge4#