My Math Forum Integrate over sphere issue (URGENT)

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 January 3rd, 2017, 07:24 AM #1 Newbie   Joined: Oct 2016 From: Sverige Posts: 28 Thanks: 2 Integrate over sphere issue (URGENT) So I'm suppose to integrate over a sphere w. radius 3. It has the surface charge $\displaystyle w = e^r * sinu * sin^2v$ To integrate I want to find: n dS, n being normal vector, dS delta surface aka. du dv. Normal vector = sphere coordinate normalized = $\displaystyle n = (sinu * cosv, sinu*sinv, cosu)$ $\displaystyle n dS = n dudv$ ?? But in my book they get: $\displaystyle ndS = (+- r^2sinu, 0, 0)$ I have no idea how they just deleted 2 out of 3 axis when integrating over a sphere. All help is appreciated, got final exam in less than a week.
 January 3rd, 2017, 08:45 AM #2 Math Team   Joined: Jan 2015 From: Alabama Posts: 2,279 Thanks: 570 In spherical coordinates, the radial axis is perpendicular to the sphere so the $\displaystyle \theta$ and $\displaystyle \phi$ components (called "u" and "v" here) are 0.

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