$\lim_{x\to\frac{\pi}{2}}\left(2cos\left(5x\right)sec\left(7x\right)\right)$

$\left(6x^5\right)\cdot\left(7x^2+9x^3-2x\right)^2$

$2xy^6dx+\left(6y^6-3\right)e^{-4x^2}dy=0$

$\frac{1}{\sin\left(a\right)}-\frac{1}{\csc\left(a\right)}$

$2y-5y$

$10^2+8-6^2$

$\frac{1}{x^2}-\frac{1}{x\cdot y}$