cnmna[ftot_] := NMinimize[{ftot, y1 > 0 && y2 > 0 && y1 + y2 <= 1 && 
       0 <= y6 && y9 >= 0}, {y1, y2, y3, t3, y4, t4, y5, t5, y6, y7, 
       t7, y8, t8, y9, y10, y11, y12, y13, y14, y15, y16, y17, y18, 
       y19, y20, y21}]
 
gg = {t3^2/(1 + 2*t3^2) - y3, t4^2/(1 + t4^2) - y4, t5^2/(1 + t5^2) - y5, 
     t7^2/(1 + t7^2) - y7, t8^2/(1 + t8^2) - y8}