$\int2\left(\cos bx\right)dx$

$\frac{1}{sen\:\left(a\right)\:cos\:\left(a\right)\:}-\frac{\cos\left(a\right)}{sen\left(a\right)}=\tan\left(a\right)$

$cos\left(x+y\right)-cos\left(x-y\right)=-2sin\left(x\right)sin\left(y\right)$

$\frac{4x}{4x}$

$xy-4y=x^5g^x$

$\frac{a}{4}^4-a^2b+b^2$

$2x^2+5x-6=0$