$2.\left(1-cos^2a\right)+cos^2a=1+sen^2a$

$\left(-8\right)\left(-8\right)\left(-8\right)\left(-8\right)\left(-8\right)\left(-8\right)$

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

$\int\frac{x^21}{x\left(x+1\right)}dx$

$-\left(x^2+3\right)^2$

$\left(1+\frac{0.06}{4}\right)^{4\cdot x}-3$

$a^2-18a+81$