Posts: 6

Threads: 2

Joined: Sep 2011

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

Posts: 850

Threads: 10

Joined: Mar 2009

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. *

Posts: 2,761

Threads: 100

Joined: Jul 2005

Quote:

10

EEX

12

CHS

g

LOG

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

Posts: 6

Threads: 2

Joined: Sep 2011

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

Regards,

Daniel

Posts: 2,761

Threads: 100

Joined: Jul 2005

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. *