$\left(1-cos^2x\right).\sec^2=\tan^2$

$a=\frac{1}{\cot^2x}+\frac{1}{\sec^2x}+\frac{1}{\csc^2x}$

$x^2y-3xy'+4y=0$

$\sin\left(x\right).\cos\left(90-x\right)=\frac{1}{16}$

$\lim_{x\to\frac{5}{3}}\left(\frac{6x^2-x-15}{12x^2+41x-35}\right)$

$2x^2-x-10$

$\int-\sqrt{9-x^2}dx$