$\frac{\sin\left(x\right)}{\cos\left(x\right)}+\frac{\cos\left(x\right)}{\sin\left(x\right)}\sec\left(x\right)\csc\left(x\right)$

$\frac{1}{4}x^2-7x+8+3x$

$\lim\:_{x\to\:-\infty}\:\frac{x^2}{e^{-x}}$

$\lim_{n\to\infty}\:\left(-2\right)^n-1$

$2sin\theta+4=3$

$\frac{cos2x+sin2x}{1+tan2x}$

$28+a^2-21a$