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binbagsss
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Question :
##u=\frac{E}{J}sin\phi + V##
Sustituting into ##(\frac{du}{d\phi})^{2}=\frac{E^{2}}{J^{2}}-u^{2}+2Mu^{3}##, and keeping only linear terms in ##V## attain ##cos \phi \frac{dV}{d\phi}=-sin \phi V+\frac{ME^{2}}{J^{2}}sin^{3}\phi##
My working: equalities given up to linear terms in V
##\frac{du}{d\phi}=\frac{E}{J}cos\phi+\frac{dV}{d\phi}##
##(\frac{du}{d\phi})^{2}=\frac{E^{2}}{J^{2}}cos^{2}\phi+\frac{2E}{J}cos\phi\frac{dV}{d\phi}##
##u^{2}=\frac{E^{2}}{J^{2}}sin^{2}\phi+2\frac{E}{J}sin\phi V##
##u^{3}=\frac{E^{3}}{J^{3}}sin^{3}\phi+3\frac{E^{2}}{J^{2}}sin^{2}\phi V##Subbing in gives ##\frac{E^{2}}{J^{2}}cos^{2}\phi+\frac{2E}{J}cos\phi\frac{dV}{d\phi}=\frac{E^{2}}{J^{2}}-\frac{E^{2}}{J^{2}}sin^{2}\phi-2\frac{E}{J}sin\phi+2M\frac{E^{3}}{J^{3}}sin^{3}\phi+6M\frac{E^{2}}{J^{2}}sin^{2}\phi V ##
Upon taking the ##cos^{2}\phi## to the other side and cancelling the ##E^{2}{J^{2}}## I have the correct answer but with the addition of the ##sin^{2} \phi## term.
But I can't see a way to justify getting rid of it.
Can anyone see where I've gone wrong?
Thanks very much !
##u=\frac{E}{J}sin\phi + V##
Sustituting into ##(\frac{du}{d\phi})^{2}=\frac{E^{2}}{J^{2}}-u^{2}+2Mu^{3}##, and keeping only linear terms in ##V## attain ##cos \phi \frac{dV}{d\phi}=-sin \phi V+\frac{ME^{2}}{J^{2}}sin^{3}\phi##
My working: equalities given up to linear terms in V
##\frac{du}{d\phi}=\frac{E}{J}cos\phi+\frac{dV}{d\phi}##
##(\frac{du}{d\phi})^{2}=\frac{E^{2}}{J^{2}}cos^{2}\phi+\frac{2E}{J}cos\phi\frac{dV}{d\phi}##
##u^{2}=\frac{E^{2}}{J^{2}}sin^{2}\phi+2\frac{E}{J}sin\phi V##
##u^{3}=\frac{E^{3}}{J^{3}}sin^{3}\phi+3\frac{E^{2}}{J^{2}}sin^{2}\phi V##Subbing in gives ##\frac{E^{2}}{J^{2}}cos^{2}\phi+\frac{2E}{J}cos\phi\frac{dV}{d\phi}=\frac{E^{2}}{J^{2}}-\frac{E^{2}}{J^{2}}sin^{2}\phi-2\frac{E}{J}sin\phi+2M\frac{E^{3}}{J^{3}}sin^{3}\phi+6M\frac{E^{2}}{J^{2}}sin^{2}\phi V ##
Upon taking the ##cos^{2}\phi## to the other side and cancelling the ##E^{2}{J^{2}}## I have the correct answer but with the addition of the ##sin^{2} \phi## term.
But I can't see a way to justify getting rid of it.
Can anyone see where I've gone wrong?
Thanks very much !
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