Consider the following statements:

1. dx / dy at a point on the curve gives slope of the tangent at that point.

2. If a(t) denotes acceleration of a particle, then ∫ a (t) dt + c gives velocity of the particle.

3. If s(t) gives displacement of a particle at time t, then ds / dt gives its acceleration at that instant.

Which of the above statements is/are correct?