## [DM15L M1B V28] All trig is in radians when in complex mode.

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[DM16 V22] CHS gives unexpected results
Joga
Posts: 13
Joined: Thu May 02, 2019 5:08 pm

### [DM15L M1B V28] All trig is in radians when in complex mode.

Hi. I seldom use trig functions and when I do, it's often radians. But I just needed to do some trig in degrees, and my DM15L gave me result in radians no matter what I did (tried grads, then degrees again, toggled all three modes, etc). The annunciator works as expected and shows nothing in degrees, or (G)RAD in the other modes. I thought the memory may be corrupt and did a reset, and degrees worked again. But, as soon as I put my DM15L in complex mode, the problem reappears. Just radians. Switching off complex mode (CF 8), and everything is fine again.

I kind of see why complex mode and radians are connected "mathematically", but I do expect keyboard calculations of trig functions to yield degrees when in that mode. So either the annunciator should "lock" to "RAD" when in complex mode, or the trig modes should work as expected.

Is it a bug, or is it me who doesn't understand how it supposed to work?

Edit, sorry, forgot to check my FW: M1B V28
dlachieze
Posts: 398
Joined: Thu May 04, 2017 12:20 pm
Location: France

### Re: [DM15L M1B V28] All trig is in radians when in complex mode.

Joga wrote:
Thu Apr 28, 2022 11:39 am
Is it a bug, or is it me who doesn't understand how it supposed to work?
This is how the HP-15C works with complex numbers.

From the HP-15C owner’s handbook:
For the trigonometric functions, the calculator considers numbers in the real and imaginary X-registers to be expressed in radians—regardless of the current trigonometric mode. To calculate trigonometric functions for values given in degrees, use ->RAD to convert those values to radians before executing the trigonometric function.
DM42: 00425 - DM41X: β00066
Joga
Posts: 13
Joined: Thu May 02, 2019 5:08 pm

### Re: [DM15L M1B V28] All trig is in radians when in complex mode.

A bit odd that the annunciator doesn't change then. I searched the handbook but didn't find any mention of it. You would expect a line about it when trig mode is discussed but couldn't find it searching for "degrees" or "grad". Which page?
HPMike
Posts: 319
Joined: Fri Jul 21, 2017 11:01 pm
Location: DFW, Texas

### Re: [DM15L M1B V28] All trig is in radians when in complex mode.

Joga wrote:
Thu May 05, 2022 1:07 am
A bit odd that the annunciator doesn't change then. I searched the handbook but didn't find any mention of it. You would expect a line about it when trig mode is discussed but couldn't find it searching for "degrees" or "grad". Which page?
Page 131, One-Number Functions, last paragraph. I have radians underlined in my manual. This is in Section 11: Calculating With Complex Numbers.
DM15L, S/N 00548. DM42, SN: 00159. DM41X, SN: 00973.