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# Derivatives

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Determine Dx Y 1. y = sin^2x + sinx^2 2. y = log(4x^2 + 1) Thanks [edited by - Gimlin on June 18, 2003 5:15:00 PM]

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I got the first one, if anyone cares its

y = sinx * sinx + sinx ^2
y''= sinxcosx + sinxcosx + cosx * 2x
y''= 2sinxcosx + 2xcosx

since sin2x = 2sinxcosx

y''= sin2x + 2xcosx.

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y = log(4x^2 + 1) (I''m assuming the log is base 10)

y'' = 8x / [(4x^2 + 1) * ln(10)].

"If I only had 6 months left to live I''d get back together with my first wife,
because 6 months with her would be like an eternity."
-Bobby Hall

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Lucky you no moderator saw this homework thread before you got the answers...

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assuming that:

sin^2x means sin^2(x) AND
sinx^2 means sin(x^2)

then the first part of #1 is as above (sin[2x]), but the second part is actually:
sin(x^2) --> 2x*cos(x^2) AND NOT 2x*cos(x)

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For future reference, homework questions are strictly prohibited unless they relate to game development AND you''ve shown some personal attempt.

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acctually they are practice questions for my exam tomorrow. I have the answers. I needed to know how to do the questions.

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I'm sure there are forums which are meant for this sort of thing. I know NRICH does up to a certain level.

http://www.nrich.maths.org.uk/

I'm not sure if it would be suitable or not, but you can always check it out. There will be american ones as well. They will help with homework, but in a constructive manner.

[edited by - higherspeed on June 19, 2003 6:06:55 AM]

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This must be homework. Thread closing now.

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Graham Rhodes
Senior Scientist
Applied Research Associates, Inc.

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