hi

i am typing a sigma (is there a shortcut ?)
then i type _
so i can write something just under the sigma

now i type a fraction
1 over sigma
and i want to write something under the sigma
so as the cursor is just after the sigma i type, as i did in former §, the character _
surprinsingly, the cursor dont go this time under the simga, but in a right bottom corner from the sigma

how can i write properly 1/sigma for x=1 to +infty with the x=1 just under the sigma ?

Sacha