Relation power composition

Question

At the bottom of the picture below you can see, that $R^2 = R \circ R$, you can also see, that $R^3$ = $R \circ R^2$. My question is, would $R^4$ be $R^2\circ R^2$ or $R\circ R^3$

Answer 1

Composition is associative, so it doesn't matter. $R^4 = R \circ R^3 = R^2 \circ R^2 = R^3 \circ R$