Ok, the problem is find the limit of x/sqrt(1-cosx) as x approaches 0 from the negative side. First I tried simply applying l'hopital's rule to see what would happen, and it didn't work. Next I tried rationalizing it by multiplying the numerator and denominator by sqrt(1+cosx), then using a trig identity (1-(cosx)^2=(sinx)^2 to get sqrt((sinx)^2) or simply sinx. Then I applied l'hopital's rule and ended up with a big mess that still ended up with 0/0. Did I miss something or do something incorrectly?