Practice problem
How many real numbers xxx are there such that 0≤x<2π0\le x\lt 2\pi0≤x<2π and cos(x)+cos(2x)+cos(3x)+cos(4x)=0\cos(x)+\cos(2x)+\cos(3x)+\cos(4x)=0cos(x)+cos(2x)+cos(3x)+cos(4x)=0?
7
8
9
10
Type a concept, like “slope” or “photosynthesis”.
