🧄Finding Arc Length and Curve Length in Spherical Coordinates

The essential role of the metric tensor, which establishes the relationship between coordinate changes and physical distance through the differential line element ( $d s^2$ ). The general line element, $d s^2=d r^2+ r^2 d \theta^2+r^2 \sin ^2(\theta) d \varphi^2$, embeds the coordinate system's necessary scale factors ( $r^2$ and $r^2 \sin ^2(\theta)$ ) to properly measure distance. For the specific curve given, the calculation simplified significantly because the radial and polar angle derivatives were zero, isolating the integration to the azimuthal motion. The final result, $L=2 \pi R_0 \sin \left(\theta_0\right)$, provides a satisfying geometric confirmation: it is precisely the circumference of the parallel circle traced out by the curve on the sphere's surface, demonstrating that the integral correctly measured one full revolution.

Finding the Arc Length in Spherical Coordinates | Animated Resultsviadean on Notion