$$\sin \alpha =\frac{2 tg \frac{\alpha }{2}}{1+tg ^2\frac{\alpha }{2}}$$



$$\cos \alpha =\frac{1-tg^2 \frac{\alpha }{2}}{1+tg ^2\frac{\alpha }{2}}$$



$$tg \alpha =\frac{2tg \frac{\alpha }{2}}{1-tg ^2\frac{\alpha }{2}}$$



$$ctg \alpha =\frac{1-tg^2 \frac{\alpha }{2}}{2tg\frac{\alpha }{2}}$$


2010-12-11 • Просмотров [ 4930 ]