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Yet another Differentiation question - HSN forum

Yet another Differentiation question

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#1Pammy

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Posted 02 February 2007 - 08:36 PM

Hello all
I'm stuck again, and any help would be appreciated

Differentiate: -2 cosec x

So I did this : = (-2 cosec x)
dy/dx = 4. -(-2 cosec x cot x)(-2 cosec x)
= 8 cosec x cot x . -2cosec x
= -16 cosec x cot x

But the answer is....... 8 cosec x cot x

Can anyone shed a little light on this for me ??
*~* Pam xxx *~*
*~* Kiss me, beneath the milky twilight, lead me, out on the moonlit floor, lift your open hand, strike up the band and make the fireflies dance, silver moon sparkling, so kiss me *~*

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Posted 03 February 2007 - 11:22 AM

You're very close, but I think the problem is how you are taking this "-2". I don't think this should actually be taken in the brackets at all, the only part that is raised to the 4th power is the cosec x part. If you leave the -2 outside all your differentation and just differentiate (cosec x)^4, then multiply by -2 at the end, then you should get the answer.

Also, the way you've multiplied out (-2 cosec x)^3 isn't quite right, you need to take everything in the bracket to the third power, so you should end up with -8cosec3x.
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#3Pammy

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Posted 04 February 2007 - 01:04 PM

Thanx very much !!
I understand where I went wrong now !!!
*~* Pam xxx *~*
*~* Kiss me, beneath the milky twilight, lead me, out on the moonlit floor, lift your open hand, strike up the band and make the fireflies dance, silver moon sparkling, so kiss me *~*

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