I'm stuck on the last three problems of my homework (Yeah almost done). We are suppose to use to the chain rule to find the derivative dy/dx. Here are the problems :

18) cube root (1 + cscx / x)

19) find dy/dx implicitly given x*siny = ysinx - x + y

20) find the equation of the normal line at x = pie/2 rad

y= sinx + cos 2x

These 3 problems make no sense to me and number 20 i have no clue where to start