/sci/ - Science & Math

how did they get from the top expression to the bottom one?
applying associativity i get
[math] \displaystyle (( (( \cdots (a_1 \circ a_2) \circ a_3) \circ \cdots) \circ a_m) \circ (((\cdots (a_{m + 1} \circ a_{m + 2} ) \circ a_{m + 3} ) \circ \cdots) \circ a_n) ) \\= (((((a_1\circ a_2)\circ a_3)\circ\cdots)\circ a_m)\circ((\cdots(a_{m+1}\circ a_{m+2})\circ a_{m+3})\circ \cdots))\circ a_n [/math]