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Mathematics 9 Online
OpenStudy (studygurl14):

HELP! ASAP! MEDAL!

OpenStudy (studygurl14):

OpenStudy (studygurl14):

@dan815 @freckles @Nnesha @satellite73

OpenStudy (studygurl14):

@satellite73 @zepdrix

OpenStudy (freckles):

have you differentiated yet?

OpenStudy (studygurl14):

no. I'm stuck at that part.

OpenStudy (freckles):

we need product rule and chain rule mainly

OpenStudy (studygurl14):

would the left-hand side be sin2y + x(cos 2y)?

OpenStudy (freckles):

\[\frac{d}{dx}(x \sin(2y)) =\sin(2y)\frac{d}{dx}x+x \frac{d}{dx}\sin(2y) \\ \frac{d}{dx}(x \sin(2y))=\sin(2y)+x \cdot 2y'\cos(2y)\]

OpenStudy (freckles):

we need chain rule for the sin(2y) part

OpenStudy (freckles):

derivative of inside * outside

OpenStudy (freckles):

(sin(2y))' = (2y)'*cos(2y) = 2y'*cos(2y)

OpenStudy (freckles):

\[(x \sin(2y))'=(y \cos(2x))' \\ \sin(2y)+2y' x \cos(2y)=(y \cos(2x))'\]

OpenStudy (freckles):

the right hand side should be a bit easier now

OpenStudy (studygurl14):

I'm confused....How'd you get (y cos (2x))'?

OpenStudy (freckles):

I think you equation is x sin(2y)=y cos(2x) right?

OpenStudy (studygurl14):

Oh, right sorry. you put it together. I thought you were saying the derivative of the left side was that, lol

OpenStudy (anonymous):

cool looking http://www.wolframalpha.com/input/?i=x*sin%282y%29%3Dy*cos%282x%29

OpenStudy (studygurl14):

Thanks. I have to go wat dinner. Hopefully I can figure out the rest myself. :/

OpenStudy (studygurl14):

eat*

OpenStudy (freckles):

k well put what you get for the right hand side and I will check it

OpenStudy (freckles):

when you get time

OpenStudy (studygurl14):

I got \(\Large\frac{dy}{dx} = \frac{-y\cos{2x}-\sin{2x}}{-\sin{2y}+\cos{2y}}\)

OpenStudy (freckles):

\[(x \sin(2y))'=(y \cos(2x))' \\ \sin(2y)+2y' x \cos(2y)=y' \cos(2x)-2 y \sin(2x) \\ y'(2 x \cos(2y)-\cos(2x))=-2y \sin(2x)-\sin(2y) \\ \] you dy.dx looks a little off

OpenStudy (studygurl14):

I changed it and ended up getting the equation y = 2x for my answer

OpenStudy (studygurl14):

(equation of line tangent to....)

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