size(200); pair z0=(0,0); pair z1=(0.5,3); pair z2=(2,1); path g=z0..z1..z2; pair d0=dir(g,0); pair d1=dir(g,1); draw(Label("$\omega_0$",1),z0-d0..z0+d0,blue+dashed,Arrow); draw(Label("$\omega_1$",1),z1-d1..z1+1.5d1,blue+dashed,Arrow); draw(z0--interp(z0,z1,1.5),dashed); draw(subpath(g,0,1),blue); draw("$\theta$",arc(z0,0.4,degrees(z1-z0),degrees(d0)),red,Arrow, EndPenMargin); draw("$\phi$",arc(z1,1.05,degrees(z1-z0),degrees(d1)),red,Arrow, EndPenMargin); dot("$z_0$",z0,SW,red); dot("$z_1$",z1,SE,red);