# HP Forums

Full Version: Getting a 35S/33S to behave
You're currently viewing a stripped down version of our content. View the full version with proper formatting.
Hello all.

Let me cite the trig issue of the 33s/35s. Although trig operations near 90 degrees are a dud, is there a means to normalise a near 90 value so that a trig function can return an accurate result? Would converting the angle from degrees to radians/grads and calculating the trig function in radians/grads help?
Try it and see.
Okie doke.
(04-24-2014 06:02 PM)Matt Agajanian Wrote: [ -> ]Although trig operations near 90 degrees are a dud, is there a means to normalise a near 90 value so that a trig function can return an accurate result?
Use $$\sin(x)=\cos(90-x)$$ and $$\tan(x)=\frac{1}{\tan(90-x)}$$.

Probably not. Replace $$90$$ by $$\frac{\pi}{2}$$ in the formulas above when using radians mode.

Cheers
Thomas
(04-24-2014 07:30 PM)Thomas Klemm Wrote: [ -> ]
(04-24-2014 06:02 PM)Matt Agajanian Wrote: [ -> ]Although trig operations near 90 degrees are a dud, is there a means to normalise a near 90 value so that a trig function can return an accurate result?
Use $$\sin(x)=\cos(90-x)$$ and $$\tan(x)=\frac{1}{\tan(90-x)}$$.

Probably not. Replace $$90$$ by $$\frac{\pi}{2}$$ in the formulas above when using radians mode.

Cheers
Thomas

Thanks! Those are normalisation techniques I can live with.
Okay here's a test:

So, what's the verdict?
(04-24-2014 10:05 PM)Matt Agajanian Wrote: [ -> ]Okay here's a test:

As the HP-11C can only handle 10 digits I assume there's a typo.
I get sin(1.566981956) = 0.9999927253. I might not get why you use different input for the 35S and the other models.

So, what's the verdict?

It appears there's a problem with small values as well.
Quote:105 * sin(0.0001)

HP-32SII 9.99999998333
HP-33S 9.99999998300
actual 9.99999998333

You could try another identity: $$\sin(x)=2\sin(\frac{x}{2})\cos(\frac{x}{2})$$.
Code:
2 / 1 ->R * 2 *
Don't search too long for ->R on the HP-35S.

Cheers
Thomas
Reference URL's
• HP Forums: https://www.hpmuseum.org/forum/index.php
• :