Question

Помогите с номером 3

Answer 1

$cosa=-\frac{3}{5}\\1) sin^{2}a+cos^{2}a=1\\ sin^{2}a=1-cos^{2}a\\ sin^{2}a=1-\frac{9}{25}=\frac{16}{25}\\ sina=+-\sqrt{\frac{16}{25} } =+-\frac{4}{5} \\ pi<n<3*pi/2 => sina=-\frac{4}{5} \\\\\\2) tga=\frac{sina}{cosa}=-\frac{4}{5}: -\frac{3}{5}= \frac{4}{5}* \frac{5}{3}=\frac{4}{3}\\3) ctga=\frac{1}{tga} =1:\frac{4}{3}=\frac{3}{4}$