SIN: f(x)= sin([math]\frac{\pi}{2}[/math] x), g(k,x,y) = f(kx)[math]\cdot[/math]f(ky)[br]a[sub]1[/sub] g(1,x,y) + a[sub]2[/sub] g(2,x,y) + a[sub]3[/sub] g(3,x,y) + a[sub]4[/sub] g(4,x,y) + a[sub]5[/sub] g(5,x,y) + a[sub]6[/sub] g(6,x,y) = 0[br][br]COS: h(x) = cos[math]\frac{\pi}{2}[/math]x), j(k,x,y) = h(kx)[math]\cdot[/math]h(ky)[br]a[sub]1[/sub] j(1,x,y) + a[sub]2[/sub] j(2,x,y) + a[sub]3 [/sub]j(3,x,y) + a[sub]4[/sub] j(4,x,y) + a[sub]5[/sub] j(5,x,y) + a[sub]6[/sub] j(6,x,y) = 0