$-4.5\:x\:2.2$

$\cos\left(x\right)\left(-\tan\left(x\right)^2\right)=\cos\left(x\right)\left(1-\sec^2\left(x\right)\right)$

$2\sin\left(2x\right)-3\sin\left(x\right)=\:0$

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

$e^{3x^2-2x}$

$\left(4x+5y\right)^2$

$\frac{dy}{dx}=24+18x+28y+21xy$