exp(-((x-4)^2+(y-4)^2)^2/1000) + exp(-((x+4)^2+(y+4)^2)^2/1000) + 0.1exp(-((x+4)^2+(y+4)^2)^2)+0.1exp(-((x-4)^2+(y-4)^2)^2)
5000-140*(x*x+y*y)+(x*x+y*y)^2
sin(x^2+y^2)/(abs(x*y)+1) from -2.5 to 2.5
(x^2+((3 y)/2-(x^2+abs(x)-6)/(x^2+abs(x)+2))^2)-36
sin(5.5x)*cos(5*y)+x*x+1 x is from -1 to 1, y is from -1 to 1, z is from 0.1 to 2.8
100-3/(sqrt(x^2+y^2))+sin(sqrt(x^2+y^2)), x is from -10 to 10, y is from -10 to 10, z is from 85 to 101
5 + (-sqrt(1-x^2-(y-abs(x))^2))*cos(30*((1-x^2-(y-abs(x))^2))), x is from -1 to 1, y is from -1 to 1.5, z is from 1 to 6
sqrt(x*x+y*y)+50*tan(sqrt(x*x+y*y))
sqrt(cos(3*x))*cos(100*y)+1.5*sqrt(abs(x)) + 0.8 x is from -1 to 1, y is from -1 to 1, z is from 0.01 to 2.5
x^2+y^2+x*y*sin(x+y) from -20 to 20
sqrt(x*x+y*y)+3*cos(sqrt(x*x+y*y))+5
((sqrt(cos(x))*cos(500*x)+sqrt(abs(x))-0.4)*(4-x*x)^0.1
