A limit is the value that a function approaches as the input value approaches a certain value.
To find the limit as x approaches 0, you can substitute 0 for x in the function and evaluate the resulting expression.
The limit of csc as x approaches 0 does not exist, since the function is undefined at x = 0.
The limit of cos as x approaches 0 is 1, since the graph of cos approaches the point (0,1) as x approaches 0.
A one-sided limit only considers the behavior of a function as the input value approaches the limit from one direction (either the left or the right). A two-sided limit considers the behavior of a function as the input value approaches the limit from both the left and the right.