Answer:
cos α = - [tex]\frac{12}{13}[/tex]
Step-by-step explanation:
Since α is in second quadrant then cosα < 0
Using the identity
sin²α + cos²α = 1 then
cosα = - [tex]\sqrt{1-sin^2\alpha }[/tex]
= - [tex]\sqrt{1-(\frac{5}{13})^2 }[/tex]
= - [tex]\sqrt{1-\frac{25}{169} }[/tex]
= - [tex]\sqrt{\frac{144}{169} }[/tex]
= - [tex]\frac{12}{13}[/tex]
