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Solving Log Eqns Simultaneously


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#1 nitrous

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Posted 06 March 2008 - 12:34 PM

Hey guys/and girls

I have a problem with solving logarithmic equations simultaneously with my Classpad. I'm using 3.02 OS.

When I try to solve the?following eqations simultaneously:

0 = A ln(4-B )
18 = A ln(6-B )

I can't seem to get a useful?decimal answer...

I tried solving them both going throgh Action>Advanced>Solve and using the simultaneous equation solving function in 2D.

Any help will be greatly appreciated. Thanks in advance :)

#2 weatherhead

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Posted 09 March 2008 - 09:47 PM

first of all, I don't know why the classpad shouldn't be able to solve this, but I think the advanced> solve command is meant for single equations, not simultaneous?? I'm not sure about this, I don't often use the CP to solve them.

Second of all, isn't this a trivially easy case to be bringing the full might of a CAS to bear on? If you look at the first equation it's clear that either A must be 0, or ln(4-B) must be 0. Since A cannot be 0 otherwise it would invalidate the second equation, then B must be 3.
Rearrange the second equation with B=3, and you get the answer for A....

I think it's probably quicker that way than to bother to type it into any computer :-)

#3 Behnoud

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Posted 10 March 2008 - 09:08 PM

I'm here just to say an unrelated observation:
Solving "~=e^(~)" take more time than "Ln(~)=~"!

#4 ECE

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Posted 12 March 2008 - 11:18 AM

Hey guys/and girls

I have a problem with solving logarithmic equations simultaneously with my Classpad. I'm using 3.02 OS.

When I try to solve the following eqations simultaneously:

0 = A ln(4-B )
18 = A ln(6-B )

I can't seem to get a useful decimal answer...

I tried solving them both going throgh Action>Advanced>Solve and using the simultaneous equation solving function in 2D.

Any help will be greatly appreciated. Thanks in advance :)


hello,
the new O.S v.3.03 solves this type of problems,
type: solve({A*ln(4-B=0,A*ln(6-B=18},{A,B})
you will get the ans.
{A=18/ln(3), B=3}.

#5 Behnoud

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Posted 12 March 2008 - 02:29 PM

It's a great improvement!
Well done CASIO!




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