Mathematics
11 Online
OpenStudy (marcelie):
Help Please !!1
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OpenStudy (marcelie):
OpenStudy (anonymous):
\[y\sin(3x)=x\cos(3y)\] right?
OpenStudy (anonymous):
diff wrt x get \[y'\sin(3x)+3y\cos(3x)=\cos(3y)-3xy'\sin(3y)\]
OpenStudy (anonymous):
btw your answer to 50 is a mistake
OpenStudy (marcelie):
oh okay ty . i fixed it lol . but ummm
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OpenStudy (marcelie):
this is what i got for 51.
OpenStudy (marcelie):
|dw:1459908990747:dw|
OpenStudy (anonymous):
is it clear how to do this implicit diff?
OpenStudy (marcelie):
thats the dy/dx right ?
OpenStudy (anonymous):
yeah i mean how to find it
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OpenStudy (anonymous):
how to get \[y'\sin(3x)+3y\cos(3x)=\cos(3y)-3xy'\sin(3y)\]
OpenStudy (marcelie):
yes thats gonna be this
OpenStudy (anonymous):
then replace \(x\) by \(\frac{\pi}{3}\) and \(y\) by \(\frac{\pi}{6}\) and solve for \(y'\)
OpenStudy (marcelie):
oh so then i plug it in directly?
OpenStudy (marcelie):
but question do i have to move some stuff ?
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OpenStudy (anonymous):
you can use algebra to solve for \(y'\) first, but it is easier just to plug in the numbers, then solve
OpenStudy (marcelie):
oh okay so then when its implicit its better to plug it in directly ?
OpenStudy (anonymous):
\[y'\sin(3x)+3y\cos(3x)=\cos(3y)-3xy'\sin(3y)\]
\[y'\sin(\pi)+3\frac{\pi}{6}\cos(\pi)=\cos(\frac{\pi}{2})-3\frac{\pi}{3}\sin(\frac{\pi}{2})\]
OpenStudy (anonymous):
i dropped a \(y'\) somewheres
OpenStudy (marcelie):
that was on the left side ?
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OpenStudy (anonymous):
\[y'\sin(\pi)+3\frac{\pi}{6}\cos(\pi)=\cos(\frac{\pi}{2})-3\frac{\pi}{3}\sin(\frac{\pi}{2})y'\]
OpenStudy (anonymous):
but now it is easy, since \(\sin(\pi)=0\) and \(\cos(\pi)=-1\)
OpenStudy (marcelie):
oh okay so i got -1/2 ?
OpenStudy (anonymous):
also \(\cos(\frac{\pi}{2}=0\) and \(\sin(\frac{\pi}{2})=1\)
OpenStudy (anonymous):
\[-\frac{\pi}{2}=\frac{\pi}{2}y'\]
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OpenStudy (anonymous):
oops another mistake damn
OpenStudy (anonymous):
\[-\frac{\pi}{2}=\pi y'\]
OpenStudy (anonymous):
so yeah, \(-\frac{1}{2}\)
OpenStudy (marcelie):
oh okay so then
OpenStudy (anonymous):
then you are done, unless you need the equation for the line
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OpenStudy (marcelie):
yes the equation
OpenStudy (anonymous):
you got the point \((\frac{\pi}{3},\frac{\pi}{6})\) and you got the slope \(-\frac{1}{2}\) use the point slope formula
OpenStudy (marcelie):
|dw:1459909748070:dw|