Прямоугольные треугольники

$$BC = \sqrt{AB^2 - AC^2} = \sqrt{(4 \sqrt{5})^2 - 8^2} = \sqrt{80 - 64} = \sqrt{16} = 4$$

$$\tg A = \frac{BC}{AC} = \frac{4}{8} = 0,5$$

$$\tg A = \frac{BC}{AC} = \frac{4}{8} = 0,5$$

$$\sin A = \frac{BC}{AB} = \frac{4}{8} = 0,5$$

$$AC = \sqrt{AB^2 - BC^2} = \sqrt{25^2 - 20^2} = \sqrt{625 - 400} = \sqrt{225} = 15$$

$$\cos A = \frac{AC}{AB} = \frac{15}{25} = 0,6$$

$$AC = \sqrt{AB^2 - BC^2} = \sqrt{(4 \sqrt{5})^2 - 4^2} = \sqrt{80 - 16} = \sqrt{64} = 8$$

$$\tg A = \frac{BC}{AC} = \frac{4}{8} = 0,5$$