Vastaus: # X = pi / 3 + 2kpi # # X = pi / 3 + 2kpi # Selitys: # 2cos ^ 2x + 3cos-2 = 0 # #sqrt (Δ) = sqrt (25) = 5 # # T_1 = (- 3-5) / 4 = -2 # # T_2 = (- 3 + 5) / 4 = 1/2 # # Cosx = 1/2 # # X = pi / 3 + 2kpi # # X = pi / 3 + 2kpi # k on todellinen