$13=7+z$

$\sin\left(\frac{\pi}{6}+x\right)+\sin\left(\frac{\pi}{6}-x\right)=\cos\left(x\right)$

$\frac{16x^8-16y^8}{3x-3y}$

$2\sin\left(x\right)\left(\csc\left(x\right)-\sin\left(x\right)\right)$

$2\left(x+1\right)^2=x^2+3x+4$

$\frac{d^8}{dx^8}\left(cos\left(4x\right)\right)$

$tanxsinx-\sqrt{3}sinx=0$