# Basic algebra but dont know what a euler number is?

• Sep 2nd 2010, 09:47 AM
Basic algebra but dont know what a euler number is?
Assume P(C2) = eP(C1) (where e is the Euler number ln(e) = 1)

And i know P(C2) + P(C1) = 1

find P(C2) and P(C1)

Thanks.
• Sep 2nd 2010, 12:12 PM
undefined
Quote:

Assume P(C2) = eP(C1) (where e is the Euler number ln(e) = 1)

And i know P(C2) + P(C1) = 1

find P(C2) and P(C1)

Thanks.

Well there are Euler numbers and then there's Euler's number. :) Here you are asked about Euler's number which is just a constant (a real number with interesting properties). What are P(Ci) supposed to represent? I don't see why it's not just a system of equations.

a = eb
a + b = 1

Find a and b.
• Sep 2nd 2010, 01:15 PM
CaptainBlack
Quote:

Assume P(C2) = eP(C1) (where e is the Euler number ln(e) = 1)

And i know P(C2) + P(C1) = 1

find P(C2) and P(C1)

Thanks.

The question tells you what e is (in this case the base for the natural logarithm)

CB
• Sep 3rd 2010, 02:29 AM
Is it lnP(C2) = P(C1)

lnP(C2) + P(C2) = 1

P(C2) = 1 and P(C1) = 0?
• Sep 3rd 2010, 06:47 AM
undefined
Quote:

Is it lnP(C2) = P(C1)

lnP(C2) + P(C2) = 1

P(C2) = 1 and P(C1) = 0?

There is a mistake with your first step, would be lnP(C2) = 1 + P(C1).

But easiest way in my opinion to start is substitution to get eP(C1) + P(C1) = 1.
• Sep 4th 2010, 03:10 AM
I don't understand :(

Whats P(C1) and P(C2) Can someone do it step by step for me please, thanks.
• Sep 4th 2010, 03:41 AM
undefined
Quote:

I don't understand :(

Whats P(C1) and P(C2) Can someone do it step by step for me please, thanks.

I asked in my first post what P(Ci) represent and you didn't respond to that, but assuming they're just real numbers,

P(C2) = eP(C1)
P(C2) + P(C1) = 1

substitute

eP(C1) + P(C1) = 1

P(C1)(e + 1) = 1

P(C1) = 1/(e+1)

then

P(C2) = eP(C1) = e/(e+1)
• Sep 4th 2010, 03:54 AM
Whats the point in telling us ln(e) = 1 , if you haven't used it?
• Sep 4th 2010, 04:10 AM
undefined
Quote:

Whats the point in telling us ln(e) = 1 , if you haven't used it?

There's no real point if P(Ci) are just real numbers but if they represent something else or if you gave us more context then maybe it would matter.
• Sep 4th 2010, 04:19 AM
Quote:

Originally Posted by undefined
There's no real point if P(Ci) are just real numbers but if they represent something else or if you gave us more context then maybe it would matter.

Ok thanks, the whole question

Consider a 2-class problem with two-dimensional features (x1,x2)transposed . The class conditional distributions P(x|Ci) are modelled by gaussian densities means = (-1,1) transposed and (1,1) transposed respectively with identical covariance matrices.

Assume P(C2) = eP(C1) (where e is the Euler number ln(e) = 1) and use the logistic discriminant fuction to derive the explicit expression of P(C1|x)
• Sep 4th 2010, 04:36 AM
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