Since \(f(0,2)=0-2=-2\), we get \(y_1=2+0.1\cdot(-2)=1.8\). Using a positive sign gives \(2.2\), and evaluating \(f\) at \(t_1\) gives a different value.
Euler's method approximates the solution of an initial value problem \(y'=f(t,y)\), \(y(t_0)=y_0\), advancing in steps of size \(h\) using the slope at the current point.