Intersection of two left cosets is empty
Clash Royale CLAN TAG #URR8PPP 2 $begingroup$ I have $theta,tau, sigmain S_7$ , where $theta=(13)(14)(567), tau=(137)(2456), sigma=(13456)(27)$ . I need to find $sigma langlethetaranglecaptaulanglethetarangle$ . I approached this by first computing $langlethetarangle$ . I got $langlethetarangle=(13)(24)(567),(576),(13)(24),(675),(13)(24)(576),id$ . I then worked out the left coset $sigmalanglethetarangle$ by multiplying $(13456)(27)$ by every element in $langlethetarangle$ , one by one. That gave me $(1574632),(134726),(274563),(1346)(257),(263)(457)$ . Using the same technique, I found $taulanglethetarangle$ to be $(357)(46),(136247),(37)(456),(1357)(246),(3647),id$ . But then I get $sigmalanglethetaranglecaptaulanglethetarangle=phi$ , since there are no elements occurring in both $sigmalanglethetarangle$ and $taulanglethetarangle$ . Why is the intersection empty? If I have done this right, is there an easier way to tell that the intersection of two cosets will be e...