mun wrote:

Good evening Sir

when we double differentiate some curve then logically it mean that we are calculating the rate of change of tangents .for examples

.when we double differentiate the curve we get the rate of change of slope negative.now according to calculus,negative rate means that something is decreasing .here rate of change of tangents is decresaing now Sir i am confused that what is really decreasing means here.?

hope sir you have understand my question as i am too confused in even asking .Show me the way by giving some practical life example.

regards and thanks

If you look at the tangent for different x's you will see that they are (for x > 0) pointing more and vertically downward as x increases. For x < 0, as x increases they tend to go from vertical upward to horizontal.

Don't try to read too much into it.