Find minimum value of 2cos x + 2cos y
values of cosines lie between -1 and +1
so minimum value of
2cosx + 2cosy
= 2(-1) + 2(-1)
= -4
when both x and y = 3π/2
so minimum value of
2cosx + 2cosy
= 2(-1) + 2(-1)
= -4
when both x and y = 3π/2