The equation of a curve is y = e^−2x tan x, for 0 ≤ x < 1/2π.

i. Obtain an expression for dy/dx and show that it can be written in the form e^−2x (a + b tan x)², where a and b are constants.

ii. Explain why the gradient of the curve is never negative.

iii. Find the value of x for which the gradient is least.