а)sina = -3/5tga = sina/cosa = 3/5 : 4/5 = 3/4 б)cosa = 5/13
tga = sina/cosa = -12/13 : 5/13 = -12/5
в)
а)
![cosa = - \sqrt{1-sin^2a} = -\sqrt{1-9/25} = -\sqrt{16/25} = -4/5](/tpl/images/0045/9018/61265.png)
![sin2a = 2sina*cosa = 2*\frac{3}{5}*\frac{4}{5} = \frac{24}{25}](/tpl/images/0045/9018/28b31.png)
![cos2a = cos^2a - sin^2a = \frac{16}{25}-\frac{9}{25} = \frac{7}{25}](/tpl/images/0045/9018/2f491.png)
![sina = - \sqrt{1-cos^2a} = -\sqrt{1-25/169} = -\sqrt{144/169} = -12/13](/tpl/images/0045/9018/570b1.png)
![sin2a = 2sina*cosa = - 2*\frac{5}{13}*\frac{12}{13} = \frac{24}{25}](/tpl/images/0045/9018/9a6e3.png)
sina = -3/5
tga = sina/cosa = 3/5 : 4/5 = 3/4
б)
cosa = 5/13
tga = sina/cosa = -12/13 : 5/13 = -12/5
в)