Mohon bantuannya ya, sebelumnya terima kasih

cosα = 15/17
Kuadran IV

sin^2 α = 1 - cos^2 α
sin^2 α = 1 - (15/17)^2
sin^2 α = 1 - 225/289
sin^2 α = 64/289
sin α = - 8/17

kuadran IV
maka nilai tanα
= sinα/cosα
= -8/17 / 15/17
= -8/15 (B)