Zgjidhja e ushtrimit 2

Vërtetoni identitetet e mëposhtme.

1. tg$A$ + cotg$A$ $\equiv$ 2cosec2$A$
2. cosec2$A$ + cotg2$A$ $\equiv$ cotg$A$
3. 2cosec2$A$ $\equiv$ sec$A$cosec$A$
4. cosec$A$ - cotg$A$ $\equiv$ tg$\frac{A}{2}$