Find the value of cosx+cos(x+2pi)+cos(x+4pi)

Question

If cosx=3.8

Answer 1

cos x = cos (x + 2π) = cos (x + 4π)

 

cos x + cos (x + 2π) + cos (x + 4π)

cos x + cos x + cos x

3 cos x

3 (3.8)

11.40