Answer :
Ballet dancers, before dancing on a smooth wooden floor they put a sticky powered called rosin on their shoes soles because the wooden floor has quite less friction and the dancer can slip and get hurt, so to avoid this, they apply those sticky powder to increase the friction between their shoe's sole and wooden floor.
And hence, they are taking advantage of frictional force.
Okay, basically they want to increase their grip and they are taking advantage of the force of friction.
I hope this helps!