Question

Помогите 2,3,5 задание пожалуйста

Answer 1

$tg2a\ ;tga=\frac{3}{5}\\tg2a=\frac{2tga}{1-tg^2a}=\frac{2*\frac{3}{5}}{1-\frac{9}{25}}=\frac{\frac{6}{5}}{\frac{16}{25}}=\frac{6}{5}*\frac{25}{16}=\frac{3*5}{8}=\frac{15}{8}$

$ctga\ ;tg\frac{a}{2}=-2\\ctga=\frac{1}{tga}=\frac{1-tg^2\frac{a}{2}}{2tg\frac{a}{2}}=\frac{1-4}{-4}=0,75$

$\frac{sin2a}{1+cos2a}=tga\\\frac{2sinacosa}{1+cos^2a-sin^2a}=tga\\\frac{2sinacosa}{2cos^2a}=tga\\tga=tga$