I never took trig in school and now I need to get some quick figures, and help in figuring out some other answers. This is not for school homework.

Q1: Take a square ABCD, bisect one side AB, and draw lines from the bisection point (A’) to the corners of the opposite side, C and D. What is angle DA’C in degrees?

Q2: How can I calculate either the angle subtended by a given line at a given distance or the ratio of the two perpendicular lines for a given angle?

What I’m looking for is a practical explanation of how to get results of the type I’ve described from a scientific calculator, keeping in mind that I know nothing about trig at all. What functions do I need to use, in what order, to get the answers to these (and similar questions.)

FYI, the practical reason for the question is that I need to know the viewing angles for people sitting at various distances from at movie theater screen. IOW: for a given screen width, at what distance does the screen fill 60 degrees of the viewer’s field of view (assuming a seat in the center)? Alternately, if the viewer is x times the screen width from the screen, what angle is his field of view?

Please keep in mind that I’m completely ignorant of trig!

Thanks.