$12.65\cdot1$

$\frac{3x-6}{x^2-5x+6}$

$\sin\left(4x\right)\cdot\sec\left(2x\right)\cdot\csc\left(2x\right)$

$x^2=y-3$

$4\left(16\right)^2$

$\lim_{x\to1}\frac{\left(x^2-x\right)\tan\left(x^{-1}\right)}{2x-2}$

$cos\left(x\right)+cos\left(x\right)cos\left(y\right)-\left(sin\left(y\right)+sin\left(x\right)sin\left(y\right)\right)y'=0$