Question

How do you differentiate `y=4/cosx`?

Answer 1

`= 4 sec x tan x`

Explanation:

`d/dx (4/cosx)`

`= 4 d/dx ((cosx)^(-1))`

`= 4 (-1) (cosx)^(-2) d/dx (cos x)`

`= -4 (cosx)^(-2) (- sin x)`

`= 4 sin x/ (cos^2x)`

`= 4 sec x tan x`