Question

sin  альфа= -0,8,<альфа<3пи/2      
найти sin альфа,ctg альфа 

Answer 1

$sin^2 alpha +cos^2 alpha =1 \ cos alpha = sqrt{1-sin^2 alpha } = sqrt{1-(-0.8)^2} = sqrt{0.36} =-0.6 \ ctg alpha = frac{cos alpha }{sin alpha }= frac{0.6}{0.8} = frac{3}{4}$