Wrong answer when evaluating log(10^-12)

[Daniel Greenidge]

Hello everyone,

I know from the power property that log(10^-12) should be -12. Wolfram-Alpha corroborates this.

However, when I evaluate this on both my HP 15C and 50g, the answer turns out to be -11. Here are the exact keystrokes I am using for my 15C:

10
EEX
12
CHS
g
LOG

Any ideas why this might be?

Thank you,
Daniel

[Bart (UK)]

Hint:


You will get the right answer if you do:

10 ENTER 12 CHS Y^X g LOG


Regards



Edit:
I should rather have said: "expected answer" above.

As Gerson says below, the answer you got is right too, to put it another way: EEX represents "10^" so 10 EEX x = 10 x 10^x = 10^(x+1)

Edited: 26 Jan 2012, 11:26 a.m.

[Gerson W. Barbosa]

Quote:

---

As Gerson says below, the answer you got is right too,

---

Bart,

I hadn't read your post yet when I said the answer of the calculator was right. "Expected answer" appears to be a more didactic expression, I should have used it myself. By the way, my HP-15C gave a lot of "wrong answers" to me, especially in the beginning, when it was just replacing a TI-59. Oh, and more recently, just some threads below my HP-42S was refusing to give me the answers I expected :-)

Regards,

Gerson.

Edited: 26 Jan 2012, 6:53 p.m.

[Gerson W. Barbosa]

Quote:

---

10
EEX
12
CHS
g
LOG

---

The answer is right. The input is wrong. You're actually entering 10*10 ^-12, that is, 10¹ * 10 ^-12 = 10^1-12 = 10^-11

Enter the mantissa first, then press EEX and enter the exponent:

1

EEX

12

CHS

g LOG

When the mantissa is 1, it can be omitted.

Gerson.

[Daniel Greenidge]

Thank you for your help! I feel a bit imbecilic right now but I certainly shall not repeat my mistake.

Regards,
Daniel