Make/N=901/D  theta1, rad1, theta2, rad2
Variable/G n1=1
Variable/G n2=1.33
theta1 = x/10
rad1 = theta1*pi/180
rad2 := asin(n1*sin(rad1)/n2)
theta2 := rad2*180/pi
display theta2 vs theta1
SetVariable setvar0 size={150,50}, font="Arial", fsize=12
SetVariable setvar0 value=n1, title="n1=", limits={1, 4, 0.01}
SetVariable setvar1 size={150,50}, font="Arial", fsize=12
SetVariable setvar1 value=n2, title="n2=", limits={1, 4, 0.01}