$\frac{dy}{dx}=\sec y$

$\frac{\csc\left(x\right)}{\sec\left(x\right)}-\frac{\sin\left(x\right)}{\cos\left(x\right)}$

$\left(-x^2+x-1\right)+\left(-x^2-2x+3\right)$

$15x\:4^2$

$\left(c^2-9\right)\left(-9-c^2\right)$

$3\sin^2\left(x\right)+4\cos^2\left(x\right)=3+\cos^2\left(y\right)$

$axdx-by^2dy=0$