S shapital May 2010 1 0 May 30, 2010 #1 Hi. How many roots (zeros) are there to the function: f(x)=a*cos(x+x1)+b*cos(2*x+x2) (a,b,x1,x2=const) in the interval [-pi,pi) ? I'm pretty sure there are either 2 or 4 roots, but I don't have any proof. Thank you for your help.

Hi. How many roots (zeros) are there to the function: f(x)=a*cos(x+x1)+b*cos(2*x+x2) (a,b,x1,x2=const) in the interval [-pi,pi) ? I'm pretty sure there are either 2 or 4 roots, but I don't have any proof. Thank you for your help.