ok, i'm just starting with this calculator, and still learning a lot (i just acquired the hp 33s). i'm trying to do this:

in DEG mode:

9 sin cos tan atan acos asin = 8.99999986001

in RAD mode:

9 ->RAD sin cos tan atan acos asin ->DEG = 9.00000000009

9 pi x 180 / sin cos tan atan acos asin 180 x pi / = 9.00000000009

does that mean RAD mode is more accurate?

thanks for the comments!

While the first step (sin) is numerically equivalent to the degrees calculation, the input angle for second step (cos) is equivalent to approximately 8.96303461718 degrees (compaired to 0.15643446504 degrees in the "degree mode" evaluation of the algorithm). Except for the first and last steps, the actual magnitude of the angles in radians for the intermediate steps are much larger than they are in "degree mode," and the algorithms used to calculate the trigonometric functions are much better behaved with those larger angles.