Evaluate: $\tan^{2}\theta - \sec^{2}\theta$

$\tan \theta=p \text { হলে, } \cos 2 \theta=\text { কত? }$

What is $\cot(\dfrac{A}{2})-\tan(\dfrac{A}{2})$ equal to ?

n যেকোনো ধনাত্মক বেজোড় সংখ্যা হলে 

$\begin{array}{l} \frac{\cos ^{4} x}{\cos ^{2} y}+\frac{\sin ^{4} x}{\sin ^{2} y}=1 \text { হলে} \frac{\cos ^{4} y}{\cos ^{2} x}+\frac{\sin ^{4} y}{\sin ^{2} x} \\\end{array}$ এর মান কত?