y1 = {-1,1} sqrt(16-x^2)/(2(abs(x) >= 2))
y2 = (2.25-abs(.75-2x^2))/(abs(x)<=1)
y3 = (x^4 + 19)/(20(abs(x) <=2)(abs(x)>= 1))
y4 = (abs(sin(pi*x)) + .5(abs(sin(pi*x/2)) - sqrt(3))/(abs(x)<=2)