Ushtrimi 4

Thjeshtoni shprehjet në vijim.

a) $\operatorname{cotg}\alpha \cdot \operatorname{tg}\alpha$

b) $\operatorname{cotg}\alpha \cdot \sin\alpha \cdot \operatorname{tg}\alpha$

c) $\cot^2 \alpha \sec \alpha \sin \alpha$

d) $\cos^2 \alpha \sec \alpha \sin^2 \alpha$