The derivative of sec x is sec x tan x = sin x/cos2x.
pi/6 = 30° for which sin is 1/2 and cos = (1/2)√3
Therefore, the derivative is (1/2)/(3/4) = 2/3
The equation of the tangent is 2/3 = [y - (2/3)√3]/[x - (π/60] which can be "massaged" into any form you need.
3/3