$\frac{1-sin^2x}{cot^2x}=1-cos^2x$

$\left(5b+11\right)\left(5b+2\right)$

$4m^2-16n^2$

$\lim_{x\to0}\left(\frac{\sin^2\left(3\cdot x\right)}{7x}\right)$

$\frac{x^2-9}{\left(x-1\right)\left(x^2-1\right)}$

$f\left(z\right)=\left(1+i\right)z^2+\left(2-i\right)z+\left(3-4i\right)$

$\left(-19m^2n^2\right)+\left(27m^2n^2\right)$