Derivative of F = Fi sin(ct): should the result be divided by c?

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agentnerdo
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Homework Statement




differentiate F=Fi (sin ct)




The Attempt at a Solution



Fi is a constant

= Fi (-cos ct)(c)

That is the solution I keep getting, but my buddy keeps getting

Fi (- cost ct)/c

in other words, he thinks - cost ct should be divided by c, anyone care to shed some light?

thanks in advance!
 
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agentnerdo said:

Homework Statement

differentiate F=Fi (sin ct)

The Attempt at a Solution



Fi is a constant

= Fi (-cos ct)(c)

That is the solution I keep getting, but my buddy keeps getting

Fi (- cost ct)/c

in other words, he thinks - cost ct should be divided by c, anyone care to shed some light?

thanks in advance!

Well neither of your solutions are correct. Your solution is the more "correct" of the two.

The derievative of sin(x) is cosx. You should not get a -cos(ct).Your buddy is indeed not differentiating; he is integrating.
 
Should be multiplied with c.

You are using the chain rule (f(g(x))' = f'(g(x))g'(x).
Here f(x) = F_i sin(x) and g(x) = cx.
Using the formula gives F_i cos(cx)*c
 
Last edited:
╔(σ_σ)╝ said:
lol. I think you need to fix your post.



Your final formula is not correct.

Wuups... It is 4:30 AM where I live :( ...
 
Inferior89 said:
Wuups... It is 4:30 AM where I live :( ...

You are completely excused !

I make these errors all the time. Too many times to be honest. :(