Zgjidhja e ushtrimit 9

Vërtetoni identitetet e mëposhtme.

1. 1 - cos2$A$ $\equiv$ tg$A$sin2$A$
2. sin2$A$(1 + tg²$A$) $\equiv$ 2tg$A$
3. cotg$A$ - tg$A$ $\equiv$ 2cotg2$A$
4. 4sin⁴$\alpha$ + sin²2$\alpha$ $\equiv$ 4sin²$\alpha$
5. sin2$\alpha$ - tg$\alpha$ $\equiv$ cos2$\alpha$ $\cdot$ tg$\alpha$
6. cos$\alpha$ $\cdot$ cosec$\alpha$ - sin$\alpha$ $\cdot$ sec$\alpha$ $\equiv$ 2cotg2$\alpha$
7. $\frac{1+tg\alpha}{1-tg\alpha}$ $\equiv$ tg(45$\degree$ + $\alpha$)