> #geodesic project sphere pictures
> with(plots):with(plottools):
Warning, the name changecoords has been redefined

> #draw the sphere only in first octant
> equator:=spacecurve([cos(t),sin(t),0],t=0..Pi/2,color=black, thickness=2):
> zerolong:=spacecurve([cos(t),0,sin(t)],t=0..Pi/2,color=black, thickness=2):
> east90long:=spacecurve([0,cos(t),sin(t)],t=0..Pi/2,color=black, thickness=2):
> north30lat:=spacecurve([sqrt(3)*cos(t)/2,sqrt(3)*sin(t)/2,1/2], t=0..Pi/2,color=blue,thickness=3):
> xaxis:=line([0,0,0],[1,0,0],color=black,linestyle=3):
> yaxis:=line([0,0,0],[0,1,0],color=black,linestyle=3):
> zaxis:=line([0,0,0],[0,0,1],color=black,linestyle=3):
> avector:=line([0,0,0],[sqrt(3)/2,0,1/2],color=green,linestyle=3):
> bvector:=line([0,0,0],[0,sqrt(3)/2,1/2],color=green,linestyle=3):
> avert:=line([sqrt(3)/2,0,0],[sqrt(3)/2,0,1/2],color=black, linestyle=3):
> bvert:=line([0,sqrt(3)/2,0],[0,sqrt(3)/2,1/2],color=black, linestyle=3):
> ahort:=line([0,0,1/2],[sqrt(3)/2,0,1/2],color=blue,linestyle=3):
> bhort:=line([0,0,1/2],[0,sqrt(3)/2,1/2],color=blue,linestyle=3):
> great:=spacecurve([sqrt(3)*cos(t)/2-sin(t)/(2*sqrt(5)), 2*sin(t)/sqrt(5), cos(t)/2+sqrt(3)*sin(t)/(2*sqrt(5))], t=0..arccos(1/4),color=green,thickness=3):
> texta:=textplot3d([sqrt(3)/2+0.1,0,1/2+0.07,"A"],font=[HELVETICA,24], color=black):
> textb:=textplot3d([0,sqrt(3)/2,1/2,"B"],font=[HELVETICA,24], color=black):
> texto:=textplot3d([0,0,0,"0"],font=[HELVETICA,24],color=black):
> display(equator,zerolong,east90long,north30lat,xaxis,yaxis,zaxis, avector,bvector,avert,bvert,ahort,bhort,great,texta,textb,texto, title="Great circle in green, 30N in blue", titlefont=[HELVETICA,24]);
>