関数の原始関数（反微分）

An antiderivative is a function whose derivative reproduces the original function, reversing the differentiation process. If you know a velocity function and need to find position, you use the antiderivative to reverse the operation. This relationship allows reconstruction of original functions from their rates of change, similar to application of antiderivatives linear motion.

Antiderivatives are not unique because differentiation eliminates constant terms. The derivatives of x² + 5, x² − 5, and x² − 7 all equal 2x. Since the derivative of any constant is zero, constant information is lost during differentiation, making multiple functions share the same derivative.

The constant of integration, represented as C, accounts for all possible functions sharing the same derivative. The general antiderivative is written as a particular antiderivative plus C, representing an entire class of functions differing only by a constant shift. This constant captures unknown initial conditions when reconstructing functions.

The power rule provides systematic formulas for finding antiderivatives of polynomial functions. These formulas enable you to work backward from derivatives to original functions efficiently, mirroring how an object's position can be inferred from its velocity over time without manual calculation.

Differentiation eliminates constant terms because the derivative of any constant is zero. This loss of constant information means that multiple functions differing only by a constant term produce identical derivatives, which is why the constant of integration must be included in the general antiderivative.

Reversing differentiation means using the antiderivative operation to recover an original function from its derivative. This reversal is essential when you know a rate of change, like velocity, but need to find the original quantity, like position. The antiderivative undoes the derivative operation systematically.

The antiderivative is essential for motion problems because it allows you to determine position when velocity is known. When a ball moves along a curved path, its velocity is the derivative of position. Using the antiderivative reverses this relationship, enabling you to reconstruct the position function from velocity data.