$\cos^2\left(\frac{\pi}{4}-x\right)-\sin^2\left(\frac{\pi}{4}-x\right)=\sin2x$

$169x^2-144$

$6x^2-36+12x$

$\left(\sqrt{2}+2\right)\:x\:\left(\sqrt{2}-2\right)$

$\int\frac{secx}{secx+tanx}dx$

$\left(x+3\right)\left(x-3\right)-\:\left(x+5\right)^2$

$\sin\left(90-y\right)+\sin\left(y\right)=1$