How do you differentiate f(x)=1/sinx-secx+tanx using the sum rule?

Rewrite $f \left(x\right) = \csc \left(x\right) - \sec \left(x\right) + \tan \left(x\right)$
$f ' \left(x\right) = - \csc \left(x\right) \cot \left(x\right) - \sec \left(x\right) \tan \left(x\right) + {\sec}^{2} \left(x\right)$
$\left(\frac{d}{\mathrm{dx}}\right) \left[f \left(x\right) + g \left(x\right)\right] = f ' \left(x\right) + g ' \left(x\right)$