654 Fermat theorem economic formulation, 30 for n variables, 97 geometrical formulation, 27 intuitive formulation, 5 one-variable problems, 15 physical formulation, 27 prehistory of, 76 rational decision maker, 29 Fermat-Lagrange condition, 427 Fermat-Lagrange theorem for pertur- bations, 428 Fermat-Torricelli point, 109 Fibonacci method, 288 first welfare theorem, 388 fish, illusion of position of, 64 flat, 236 flows of cargo, prediction of, 370 formula, solution set linear system, 507 four-step method basic form, 111 userfriendly version, 20 INDEX Hamiltonian function, 500 Hessian, 263 hidden convexity, 257 hinged quadrangle, 160 paradox, 195 HJB equation, 445 Huygens, pendulum clock of, 406 ice cream cone, 339 identity matrix, 510 implicit function theorem, 168 incentives, may fail, 160 inconsistency, time, 496 inequality arithmetic-quadratic means, 156 between l p -norms, 157, 197 Cauchy-Bunyakovskii-Schwarz, 89 geometric-arithmetic means, 31 geometric-quadratic means, 154 Hadamard, 197 triangle, 89 infimum, 520 inflation, low, 497