Question

Help please, thank you so much

Answer 1

Explanation:

theta lies in 3rd quadrant so cos \theta is negative.

`cos \theta=-√(1-sin^2 \theta) \\=-\sqrt{1-(-(15)/(17) )^2} \\=-\sqrt{1-(225)/(289) } \\=-\sqrt{(289-225)/(289) } \\=-\sqrt{(64)/(289) } \\=-(8)/(17)`