Hello from MrBillDoesMath!
Answer:
-5/12
Discussion:
if sin(a) = -5/13 then the underlying triangle is a 5, 12, 13 right triangle. From the Question, the angle lies in the third quadrant.
Hence cos(a) = 12/13 and
tan(a) = sin(a)/cos(a) = (-5/13)/ (12/13) = -5/12
Regards,
MrB
P.S. I'll be on vacation from Friday, Dec 22 to Jan 2, 2019. Have a Great New Year!
