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Find [tex] \frac{dy}{dx} \; \; \; xtanx \; \; \; dx [/tex]

The standard differential is given in the formula book as

[tex] f(x) = \tan kx \Rightarrow f'(x) = k\sec^2 kx [/tex]

Therefore, I got:

[tex] \frac{dy}{dx} = x \sec^2 x [/tex]

However, the answer given is

[tex] \tan x + x \sec^2 x [/tex]

I can't see where I've gone wrong, it seems like such a simple differential. Any help would be much appreciated.

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# Homework Help: Differentiation of Trig Functions

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