complementary forms

[hhtt21]

"The governing equations of fluid flow can be written in two forms, the differential form and the integral form. These two forms are complementary."
https://confluence.cornell.edu/display/SIMULATION/Big+Ideas:+Fluid+Dynamics

Which of the definitions in the link fit for complementary used above?

https://www.merriam-webster.com/dictionary/complementaryThank you

 

[SoothingDave]

https://www.merriam-webster.com/dictionary/complementary

Definition 4 here, leading to:

https://www.merriam-webster.com/dictionary/complement#h1

Defintion 1c here.