Re: HP 30B Keyboard Overlay ... really? Message #18 Posted by Jim Yohe on 7 Nov 2010, 11:40 p.m., in response to message #12 by gene wright
Hey Gene, I'm not sure if I found the two errors you are referring to in this one learning module or of there is another one that I haven't run across yet but in the "HP30b 33Trigonometry.pdf" file Example 4 has compound problems.
The solution is flawed in two ways. In this example the author creates an input to the arcsine (ASIN) function that falls outside of its domain and so therefore fails. The user is instructed to divide 6 by 3 which results in 2 and to take the arcsine of this number. The valid domains for arcsine (ASIN) is (1,+1), arccosine (ACOS) is (1,+1), and arctangent (ATAN) is (infinity,+infinity) so 2 clearly falls outside of ASIN's domain of (1,+1).
Now to identify the real problems:
1) You are given only dimensions for the (opposite and adjacent) sides of this right triangle not the (opposite and hypotenuse) sides which is required by the arcsine function. The only function that will work with these two sides is arctangent;
2) If you are to use this function and the angle is from the ladder to the wall (up where the ladder contacts the wall), then you need to divide 3 by 6 not the original 6 by 3.
Therefore the solution is:
Angle = ATAN(opposite/adjacent) = ATAN(3/6) = ATAN(0.5) = 26.56 degrees
