What is the result of the integral ∫ tan^2(x) dx?

To find the result of the integral ∫ tan²(x) dx, it's useful to recall that tan²(x) can be expressed in terms of sec²(x) using the identity tan²(x) = sec²(x) - 1. This transforms the integral as follows:

∫ tan²(x) dx = ∫ (sec²(x) - 1) dx = ∫ sec²(x) dx - ∫ 1 dx.

The integral of sec²(x) dx is well-known and equals tan(x), while the integral of 1 dx is simply x. Thus, we can evaluate the integral:

∫ tan²(x) dx = tan(x) - x + C.

The constant C accounts for the constant of integration.

The answer is therefore expressed correctly as tan(x) - x + C, which corresponds to one of the choices provided. This integrates the trigonometric function appropriately and aligns with the standard integral results known for these functions.