SOLUTION: How many zeroes does {{{y = 12/cos (4x) + 4}}} have, between 0 and 2pi ?

It does not have any zeros,

Since cos(4x)is always between -1 and +1, the first term has smallest
positive velue when cos(4x) = 1 which gives , so 16
is the minimum positive value.  The first term has largest negative value 
when cos(4x) = 1 which gives , so -8 is the maximum 
negative value.  The graph never crosses the x-axis and thus there are
no zeros at all.



Edwin