Прямоугольные треугольники

$$BC = AC \cdot \tg A = 0,5 \cdot \frac{\sqrt{1 - \cos^2 A}}{\cos A} = 0,5 \cdot \frac{\sqrt{1 - \frac{17}{289}}}{\frac{\sqrt{17}}{17}} = 0,5 \cdot \frac{\frac{4\sqrt{17}}{17}}{\frac{\sqrt{17}}{17}} = 0,5 \cdot 4 = 2$$

$$AC = AB\cdot\cos A = 5\cdot\sqrt{1 - \sin^2A} = 5\cdot\sqrt{1 - \left(\frac{7}{25} \right)^2} =$$

$$= 5\cdot\sqrt{1 - \left(\frac{49}{625} \right)} = 5\cdot\sqrt{\left(\frac{576}{625} \right)} = 5\cdot\left(\frac{24}{25} \right) = 4,8$$

$$BC = AB\cdot\sin A = 8\cdot0,5 = 4$$

$$AC = AB\cdot\cos A = 8\cdot0,5 = 4$$

$$BC = AB\cdot\sin A = 5\cdot\sqrt{1 - \cos^2 A} = 5\cdot\sqrt{1 - \left(\frac{7}{25}\right)^2} =$$ $$= 5\cdot\sqrt{\frac{576}{625}} = 5\cdot\frac{24}{25} = 4,8$$