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# C3 Exponential Functions watch

1. I'm so confused: the book says the inverse of e^x is lnx....ok I know this is obviously correct....but surely if y = e^x, then the inverse should be Iny ???? Please help

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2. you got it horribly wrong.
-e^ln(x) = x
-if y = e^x, x = ln y
3. (Original post by anoymous1111)
I'm so confused: the book says the inverse of e^x is lnx....ok I know this is obviously correct....but surely if y = e^x, then the inverse should be Iny ???? Please help

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An inverse function is a reflection in the line y=x. For this reason, when you say that

you need to swap x and y to get the correct inverse function (as a function of x).
4. (Original post by shawn_o1)
you got it horribly wrong.
-e^ln(x) = x
-if y = e^x, x = ln y
Isn't the second bit what I said? oh god I just don't get it at all

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5. (Original post by Indeterminate)
An inverse function is a reflection in the line y=x. For this reason, when you say that

you need to swap x and y to get the correct inverse function (as a function of x).
Ahhhh ok that makes sense! Im just missing the whole point!

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6. (Original post by anoymous1111)
Ahhhh ok that makes sense! Im just missing the whole point!

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Kind of like how you say the inverse of is not . (for the nitpickers, assume a suitably picked domain to make x^2 injective.)
7. (Original post by Zacken)
Kind of like how you say the inverse of is not . (for the nitpickers, assume a suitably picked domain to make x^2 injective.)
Ah god I don't know how the hell I misunderstood so much! Thank you!!!

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8. (Original post by anoymous1111)
Ah god I don't know how the hell I misunderstood so much! Thank you!!!

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Don't fret it, it's better than you come on here and make an effort to understand it. I admire that! Most people simply shrug and don't bother trying to understand. :-)
9. (Original post by Zacken)
Don't fret it, it's better than you come on here and make an effort to understand it. I admire that! Most people simply shrug and don't bother trying to understand. :-)
Awww that makes me feel better! Thank you!

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10. (Original post by anoymous1111)
Awww that makes me feel better! Thank you!

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You're welcome!
Feel free to post whenever you have a question!

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