1. The problem statement, all variables and given/known data Un a sequence 0 < x < pi/2 U0 = 2cosx Un+1 = quroot( 2 + Un) 1) Calculate U1, U2, and U3 in function of x (simplify maximum) 2) Show that Un = 2cos( x / 2^n) 2. Relevant equations 3. The attempt at a solution 1) U1 = sqroot( 2 + 2cosx) = sqroot( 2 (1 + cosx)) = ?? (now , how do i simplify) because , i should have when i have simplified a maximum : U1 = 2cos(x/2) = 2 (2cosx² - 1) = 4cosx² - 2 So how do i go from sqroot( 2 + 2cosx) to 4cosx² - 2 ??