How can I minimize the approximation ? Before doing the problem, I had to solve the equation but to solve it, I had to approximate sin(x)=x. Else, it's impossible to solve! The solution is Theta(t)= -30*cos(sqrt(9.81/2)*t)+B*sin(sqrt(9.81/2)*t). When I use, my solution, I have a tiny error that makes a tiny difference with the expected result and that count this as a false solution. What am I doing wrong ?