HintHint!! 

Find the pair of reals (x_{1},x_{2}), x_{i} Î [5,+5] minimizing the expression 20 + x_{1}^{2} + x_{2}^{2} 10 * (cos(2 px_{1}) + cos(2 px_{2}))Let's use the environment for such a task; for this, we well use the two rows of Tabs you can see in GUIDE's GUI: on the first row three tabs are proposed:
fit = 20 + theGenome.var1 ^ 2 + theGenome.var2 ^ 2; fit += 10 * cos(2 * pi * theGenome.var1); fit += 10 * cos(2 * pi * theGenome.var2);Other ways of treating the fitness function will be detailed later in this Document.