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Any mathematicians here?

Question:

Something I've never quite understood was the reasoning behind this certain aspect of trig notation:

ex: differentiate sin^3 e^x

The first thing you'd do is rewrite this as (sin e^x)^3 such that you can easily differentiate with the chain rule.

I see this all the time...why is it not just written with the cube applied to whole expression on the outside of the expression to begin with?

Too many profs answer "well that's the way it is".

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Old 01-11-2015, 10:54 AM
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simpler to do it the other way (fewer keystrokes) and if it's an agreed upon notation that everyone understands....
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Old 01-11-2015, 12:32 PM
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Quote:
Originally Posted by BGCarrera32 View Post
Question:

Something I've never quite understood was the reasoning behind this certain aspect of trig notation:

ex: differentiate sin^3 e^x

The first thing you'd do is rewrite this as (sin e^x)^3 such that you can easily differentiate with the chain rule.

I see this all the time...why is it not just written with the cube applied to whole expression on the outside of the expression to begin with?

Too many profs answer "well that's the way it is".
sin is a function, and exponentiation is also a function. Every function has to have an argument to work on,

in sin θ, it is clear that sin is the function and θ the argument
in x^n, it is clear that x is the argument and ^3 is the function

In the same way it was traditionally agreed that exponentiation of a trig function can be written sin^n θ or as (sin θ)^n, because mathematicians are basically lazy and don't like to write anything extra


in sin^3, ^3 is not not an argument, it is itself a function w/ sin something as it's argument,

the rewrite is just a clearer way to represent the same thing
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Old 01-11-2015, 12:39 PM
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^^I was gonna say the same thing, but Bill beat me to it
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Old 01-11-2015, 04:26 PM
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Quote:
Originally Posted by Bill Verburg View Post
sin is a function, and exponentiation is also a function. Every function has to have an argument to work on,

in sin θ, it is clear that sin is the function and θ the argument
in x^n, it is clear that x is the argument and ^3 is the function

In the same way it was traditionally agreed that exponentiation of a trig function can be written sin^n θ or as (sin θ)^n, because mathematicians are basically lazy and don't like to write anything extra


in sin^3, ^3 is not not an argument, it is itself a function w/ sin something as it's argument,

the rewrite is just a clearer way to represent the same thing
Thank you Bill.
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Old 01-11-2015, 05:15 PM
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Whew! For a minute I thought this was going to be another question about what 48/2(9+3) is again (which everyone knows is 288)
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Old 01-11-2015, 08:25 PM
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Bill is more than just another pretty face !!
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Old 01-11-2015, 08:47 PM
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Bill is more than just another pretty face !!
Now I know how he can understand all those Porsche transmission graphs.
Old 01-12-2015, 01:38 PM
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So you don't need parenthesis to clarify?

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Old 01-12-2015, 04:08 PM
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