Question

Прошу, помогите мне!

Answer 1

$cos alpha =-frac{8}{17}\\pi textless alpha textless frac{3pi }{2}; ; Rightarrow ; ; sin alpha textless 0\\sin^2 alpha =1-cos^2 alpha =1-frac{64}{289}=frac{225}{289}\\sin alpha =-sqrt{frac{225}{289}}=-frac{15}{17}$