Questions tagged [inverse]

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32 votes
5 answers

Why are there two inverses to exponentiation?

I'm not sure if this is more educational or more "pure math", but: For multiplication and addition, there is exactly one inverse operation, namely division and subtraction. For ...
8 votes
9 answers

Method of Solving $5^x=326$ (Logs not allowed)

$5^x=326$ A book titled "algebra and trigonometry" by Paul Foerster, offers this problem. It came before the logarithm chapter and specifically said not to solve with any log manipulation. It ended ...
8 votes
3 answers

What are some common ways students get confused about finding an inverse of a function?

What are some common ways students get confused about finding an inverse of a function? One I can think of is conflating multiplicative inverses of rational numbers with functional inverses. e.g. ...
7 votes
2 answers

Why bother calculating the inverse of 3 by 3 matrix?

My government has told me that I must teach 17 year olds how to invert a 3 by 3 matrix using adjoints/cofactors, without using any technology. Is there any reason why you would want to know how to do ...
6 votes
3 answers

Apply the inverse operation on both sides, or know the inverse function?

My old question here was about logarithms, but as I teach more and more (precalculus) algebra, I've generalized the question a bit in my mind. Should students do the same thing to both sides, or ...
7 votes
1 answer

Why many people believe that: $\displaystyle c>0\implies \frac{1}{c}<0$?

I came across many people who believe the below false implication. I don't know why people believe it true in high school and middle school and also students in university level. Really I would like ...
13 votes
2 answers

Logarithm Tables - How were the values reached?

I'm teaching an Algebra II/Trigonometry class that is currently working on logarithms as the inverse function of exponential functions. Now, to keep their interest I had them struggle for a few ...