Well I was given this question for homework and while I think I understand the trigonometry side of things. I think I have to use periodic functions (and graphics calculator) to solve this question, but Im not entirely sure. Its really stumped me because I've missed a few lessons and it'll probably be on the next test.

The question follows:

"A soccer field is 100 metres long and 40m wide. There is an 8m goal on the shorter ends of the field. When a penalty is awarded for a serious infringement, a player from the opposing team may take a free shot at goal from anywhere along the sideline.

Officials decide to change the rules so that the penalty shot must be taken from a position inside a rectangular box. The box is centred on the halfway line shown in the diagram. What is the size of the box if the shooting angle (see diagram) inside the box is less than 9o and greater than 16o."

I'm guessing that I have to use trig to find the shooting angles from a point and somehow turn it into a periodic function which I can plot into my graphics calculator