When a certain polygon is rotated 60° counterclockwise, it is carried onto itself. What Shapes are These?

One expression below in undefined, and the other expression has a well defined value. which expression is undefined and explain why it has no value. which expression is defined? what is the value of that expression and how do you know? what is a different expression using a trig inverse function that is also undefined?

Which of the following would be a good name for the function that takes the weight of a box and returns the energy needed to lift it?

Solve the following simultaneous equation by using an algebraic method (either substitution or elimination) 2x + 3y=-4 4x-y=11