Equivalent expression for sinx^3

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SUMMARY

The discussion focuses on finding an equivalent expression for sin(3x) using only first powers of sin(x), sin(2x), and sin(3x). Participants clarify that the initial approach using sin(x) and sin(2x) is not aligned with the requirement of expressing sin(3x) solely in terms of first powers. The correct method involves utilizing the sine addition formula and recognizing that sin(3x) can be expressed as 3sin(x) - 4sin^3(x). This approach adheres to the constraints set by the problem statement.

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synergix
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Homework Statement


Find an equivalent expression for sin3x in terms of function values of x, 2x, 3x, raised only to the first power.


The Attempt at a Solution


stuck! don't know where to begin I am reviewing for my exam right now I remember doing one of these problems before but I can't remember how.

sinx(sinx2)

sinx[(1-cos2x)/2]

am i on the right track?
 
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synergix said:
Find an equivalent expression for sin3x in terms of function values of x, 2x, 3x, raised only to the first power.

stuck! don't know where to begin I am reviewing for my exam right now I remember doing one of these problems before but I can't remember how.

sinx(sinx2)

sinx[(1-cos2x)/2]

am i on the right track?

Hi synergix! :smile:

(btw, don't write (sinx2), write either (sinx)2 or sin2x)

Your equation is correct, but I don't think it's what they're asking for …

it has a (sinx)(cos2x) … if you're allowed that, you might as well have (sinx)(sinx)(sinx).

I think they want a sum of first powers, each on its own.

Hint: start at the end …

what is sin(3x) in terms of powers of sinx? :wink:
 

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