Rotation of $u_1$ around $q_1$(unknown) axis is $u_2$, and rotation of $u_2$ around $q_2$(unknown) axis is $u_3$. What is the value of axis $q$,in case $q$=$q_1$=$q_2$?
Note that possible values of $q_1$ makes a circle,$c_1$, in 3d space,and $q_2$ another circle,$c_2$, in 3d space. Question is to find the intersection($q$,unit vector) of these circles, $c_1$ and $c_2$.
related to question in find quaternion scalar from end points of the rotation