Hi folks,

Given $y = e^x \tan x$ we have to show that $\dfrac{d^2 y}{dx^2} = e^x (2 \tan^3 x + 2 \tan^2 x + 3 \tan x + 2)$

now I get $\dfrac{d^2 y}{dx^2} = e^x (2 \sec^2 x \tan x + 2 \sec^2 x + \tan x)$

so somehow $2 \sec^2 x \tan x + 2 \sec^2 x + \tan x = 2 \tan^3 x + 2 \tan^2 x + 3 \tan x + 2$

I have been horsing around for ages not getting there. A hint would be nice, lest I die of old age.

Thanks