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Mathematics 15 Online
OpenStudy (marcelie):

help please.. find the length of the curve

OpenStudy (alivejeremy):

o-o

OpenStudy (marcelie):

let\[y=\frac{ x^4 }{ 16 } +\frac{ 1 }{ 2x^2 }\]

OpenStudy (marcelie):

1 </ x </ 2

OpenStudy (marcelie):

so far i have this \[\int\limits_{1}^{2}\sqrt{\frac{ 1 }{ 2 }+\frac{ x^6 }{ 16 }+x ^{-6}} dx\]

OpenStudy (marcelie):

i simplified it which my derivative was \[\frac{ dy }{ dx }=\frac{ 1 }{ 4 }x^3-x ^{-3}\]

zepdrix (zepdrix):

When you squared the y' you ended up with,\[\large\rm (y')^2\quad=\quad \frac{x^6}{16}\color{orangered}{-\frac12}+x^{-6}\]Right? And now you have a +1/2 in the middle instead of -1/2 when you add the 1. Remember this little trick?

OpenStudy (marcelie):

uhhhh LOOl which trick D:

zepdrix (zepdrix):

Your derivative squared gave you this,\[\large\rm \frac{x^6}{16}\color{orangered}{-\frac12}+x^{-6}\quad=\quad \left(\frac{x^3}{4}-x^{-3}\right)^2\]So then how bout this?\[\large\rm \frac{x^6}{16}\color{royalblue}{+\frac12}+x^{-6}\quad=\quad \]

OpenStudy (marcelie):

like this D: |dw:1482211867285:dw|

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