Abstract. Littlewood in his 1968 monograph “Some Problems in Real and Complex Analysis” [9, problem 22] poses the following research problem, which appears to still be open: “If the nm are integral and all different, what is the lower bound on the number of real zeros of PN m=1 cos(nmθ)? Possibly N − 1, or not much less.” Here real zeros are counted in a period. In fact no progress appears to h...