In working with spherical coordinates $\rho$, $\phi$,$\theta$, where $\phi$ is the spherical angle, one could plot a simple flat plane in the space of the spherical coordinates.
For example:
In the basis ($\rho$, $\phi$,$\theta$), I have three points. They are (1,0,0), (0,$\pi/2$,0), (0,0,$\pi/4$). Clearly these 3 points define a plane/triangular region in this basis.
My question is, however, what does this region look like in cartesian space? Is it simply a spherical patch of area?
Is the area of this region given by one half the cross product of the vectors:
Area = (1/2) | (<1,0,0> - <0,$\pi/2$,0>) x (<0,0,3> - <0,$\pi/2$,0>) |?
I have been thinking about this for quite some time now and have not yet come up with an answer. Help would be appreciated.