plot3d_spherical(1, (theta, 0, 0.7 * pi), (phi, 0, 1.8 * pi))
# Expected:
## Plot object containing:
## [0]: parametric cartesian surface: (sin(theta)*cos(phi), sin(phi)*sin(theta), cos(theta)) for theta over (0, 0.7*pi) and phi over (0, 1.8*pi)