what is the derivative of y= 2ln(secx) at x=pi/4
y = 2 ln (sec x)
dy/dx = 2 [tan^2x]/ secx = 2 [secx tanx] / secx = 2 tan x
So at x = pi/4....we have
y '(pi/4) = 2 tan (pi/4) = 2 * 1 = 2
