Easter Sunday Trigs ( rpn38-CX)

[bshoring]

Thanks for the insight. This satisfies my curiosity that one can compute Sine, Cosine and Tangent using the Net Present Value function.

Here's my short little program based on your knowledge and hard work!

Trig using NPV

Angles in Degrees

R/S --> cos(x)
R/S x<>y --> sin(x)
R/S / --> tan(x)

Constants:

n: 9
R0: 0
R1: 1
R2: 0
R3: -0.166666666666667
R4: 0
R5: 8.333333204E-3
R6: 0
R7: -1.98410348E-4
R8: 0
R9: 2.742018422E-6
R.9: 1.74532925199433e-2

01 - 86 61 9 RCL × .9
02 - 1 1
03 - 24 23 ∆%
04 - 12 i
05 - 24 13 NPV
06 - 31 ENTER
07 - 31 ENTER
08 - 61 ×
09 - 32 CHS
10 - 1 1
11 - 51 +
12 - 24 21 √x
13 - 25 7 00 GTO 00

On RPN-38 CX, it only takes 12 program steps. On my original HP-38C, with slight modification, it also works quite nicely, with similar results. So far the NPV route isn't producing quite the level of accuracy that your fine programs do, but I do find it exciting to think that a built in financial function can be used this way!

If run on an actual HP-12C or HP-38 E/C, the first line could be replaced with 2 lines:
RCL FV
X
(And the constant 1.745329252E-6 needs to loaded into the FV register).