@Mariusz Iwaniuk 

Thank you!

@Kitonum 

Thank you!

@acer 

I understood! Thank you!

@Kitonum , thanks!!!

But there is a problem with recursion. The values ​​of P(t) should be from 0 to 10:

1,1.11027817171800, 1.11920941811229, 1.12821250479788, 1.13728790120588, 1.14643623853666, 1.15565811900633, 1.16495422889185, 1.17432523278786, 1.18377169497893,1.19329419324130.

However, the recursive issue is generating an incorrect result:

[1], [2.500000000], [1.000000000], [2.504200000], [.9999966385], [2.508408403], [0.9999899060], [2.512625229], [.9999797850], [2.516850495], [.9999662635].

I do not know what else to do...

And if,

eqns := {a(i + 1) = (1 + 10^(-5)*(0.01*i - 0.007)/0.0001)*a(i) + 0.1*10^(-5)*c(i), c(i + 1) = 0.01*10^(-5)*i/0.0001*a(i) + (1 - 10^(-5))*0.1*c(i)} ?

@acer 

Thanks!

However, in this way, how can I parameterize the functions Ap and Cp? 

@dharr 

Thanks!

thank you all!

@Kitonum 

guys, I think I found the solution;

diff(eval(ln(piecewise(0 <= t, 2 + 5*t)), t = 0), t)

0

@Kitonum

ok, however,

 in t=0, ln (2) = 0,69314718055

and 

diff (ln(2)) = 0

@Carl Love 

Thank you!!!!

@tomleslie 

Ok! Thank you!

@acer 

Thank you!!!

@Kitonum 

Thank you!!!

@mmcdara 

Thank you so much!!!