Originally Posted by

**PatrickM** I'm doing some revision and I'm having some trouble understanding the principle behind picard's iteration.I tried to do some practice by tackling the following problem but I got nowhere as I don't know with what should I substitute f(s,u(s)) in the integral.

The problem states the following:

u'= v and v'= −u

with initial conditions u(0) = 1 and v(0) = 0, find an approximate solution by

performing 4 steps of Picard iteration and compare the results with the actual solution.

If someone has the time and patience to enlighten me with a step by step explanation that will be incredible.

Thanks at least for taking the time to read this