`y = e^x / x , (1, e)` Find an equation of the tangent line to the given curve at the specified point.
The slope of the tangent at a point is equal to the derivative of the given function at that point.
At (1,e) the derivative is equal to 0.
The slope of the tangent is equal to zero.
The equation of tangent is equal to y-e=0(x-1)
that is y=e.