$\lim_{x\to\frac{\pi}{2}}\left(9\cos\left(-3x\right)\sec\left(9x\right)\right)$

$\lim_{x\to0}\left(\frac{x^3-x^2-x+1}{sin^2\left(\pi x\right)}\right)$

$-11k+13-g+5g+7+3k$

$\csc\left(y\right)+\sec^2\left(x\right)\frac{dx}{dy}=0$

$-5\sqrt{48}+\sqrt{12}$

$-10=3x-x^2$

$\frac{d}{dx}\frac{2xy}{1-x^2}$