Explicit Runge-Kutta method
= Explicit Runge-Kutta method
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An explicit Runge-Kutta method has $a_{ij}=0$ whenever $j\geq i$. Its stage <matrix> is strictly lower triangular: compute each <Runge-Kutta stage> using already known slopes, starting with $Y_1=y_n$. In contrast, an <implicit Runge-Kutta method> requires solving coupled stage equations, whose existence is addressed by <stage solvability of an implicit Runge-Kutta method>.