in f(x)=8+11 cos π/7 (x-2). find the first 3 positive values of x for whitch y=0

Answer 1

Just solve the equation

8+11 cos π/7 (x-2) =0

cos π/7 (x-2) =-8/11

π/7 (x-2) =arccos(-8/11)

x =(7/π) arccos(-8/11)+2+2Pi c, c is integer.

Now for every c you can find positive solution

From here you get