$\lim_{x\to0}\left(\frac{13^x-11^x}{x}\right)$

$\sec\left(y\right)dx+\csc\left(x\right)dy=0$

$\frac{\cot^2\left(x\right)}{\csc^2\left(x\right)+\sec^2\left(x\right)}=\cos^4\left(x\right)$

$3x-7<-2$

$\lim_{x\to\infty}\left(\frac{e^x}{2x^3}\right)$

$a^2.b^4-4$

$\ln\left(y\right)=.693-2x$