The motion of the particle is  and it reaches a point is .

- coordinate is decreasing at a rate of  cm/sec.

That is  cm/sec.

Here negative sign indicates decreasing nature.

Consider .

Differentiate  on each side with respect to .

.

Product rule of derivatives: .

.

Substitute  and  in above expression.

Therefore, - coordinate is increasing at a rate of  cm/sec.

- coordinate is increasing at a rate of  cm/sec.