Question

помогите решить .....................

Answer 1

$sin alpha=dfrac{sin alpha}{1} =dfrac{2sinfrac{alpha}{2}cosfrac{alpha}{2}}{cos^2frac{alpha}{2}+sin^2frac{alpha}{2}}=dfrac{2mathrm{tg}frac{alpha}{2}}{1+mathrm{tg}^2frac{alpha}{2}}=dfrac{2cdot0.5}{1+0.5^2}=dfrac{1}{1.25}=0.8$

$cos alpha=dfrac{cos alpha}{1} =dfrac{cos^2frac{alpha}{2}-sin^2frac{alpha}{2}}{cos^2frac{alpha}{2}+sin^2frac{alpha}{2}}=dfrac{1-mathrm{tg}^2frac{alpha}{2}}{1+mathrm{tg}^2frac{alpha}{2}}=dfrac{1-0.5^2}{1+0.5^2}=dfrac{0.75}{1.25}=0.6$

$mathrm{tg}alpha =dfrac{sinalpha }{cosalpha } =dfrac{0.8}{0.6} =dfrac{4}{3}$