Hi Al,

It would help if you gave us the context — it sounds like a homework question, but unless we know what skills are being taught we cannot offer you much help. Your expression equals tan 20 (because you can multiply top and bottom by sqrt(1 - cos 40)). Although 20 is one-third of a nice angle, there exists no simple formula for the tangent of 1/3 of an angle. In other words, you would probably consult your calculator to determine the value of tan 20. (Of course you could have used your calculator from the start, so I don’t see the point.)

Chris