# difficulty with model containing sine function

**URL:** <https://forum.certara.com/t/difficulty-with-model-containing-sine-function/2427>\
**Category:** Modelling and Simulation\
**Created:** [June 5, 2012, 2:22pm UTC](https://forum.certara.com/t/difficulty-with-model-containing-sine-function/2427 "2012-06-05T14:22:26Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![sampson0712](https://avatars.discourse-cdn.com/v4/letter/s/e68b1a/32.png) [@sampson0712](https://forum.certara.com/u/sampson0712)\
**Post date:** [June 5, 2012, 2:22pm UTC](https://forum.certara.com/t/difficulty-with-model-containing-sine-function/2427/1 "2012-06-05T14:22:26Z")

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Hi, I am attempting to evaluate the following model. It iterates fairly quickly in the status window, however, even after overnight running, it gets stuck at an iteration and does not proceed from there. Do you see any problems with the code below? Thanks, Mario – test(){ #recycling from cmt2 to cmt1 FT = sin((2_3.14159_(t+u)/p)) #where u is the time delay of the period (p) from the first dosing time Fpos=FT if (FT \< 0) {Fpos=0} #differential equations deriv(Aa = - (Aa \* Ka)) deriv(A1 = - (Cl \* C1) + (Aa \* Ka)- (Cl12 \* C1) + (Cl21 \* C2)- (Cl13 \* C1) + (Cl31 \* C3)) deriv(A2 = (Cl12 \* C1) - (Cl21 \* Fpos \* C2)) deriv(A3 = (Cl13 \* C1) - (C3 \* Cl31))