is tan and tan-1 the same?

NO !!!!!!!!!

The tangent of an angle returns the value for that angle [where the tangent is defined ]

Tan^-1  is the arctangent (also called the tangent inverse)....and  this returns the angle back to us

Here's an example

tan(60°) = √3

But

tan^-1 (√3 ) = 60°

See the difference ??

On the web2 calc tan^-1 is atan

arc tan is the same as inverse tan