Answer:
Cos y = t / 8
Explanation:
Using the hints given in the question, the omitted tribagke will look like the triangle attached on the picture ;
From trigonometry :
Sin y = opposite / hypotenus
Sin y = s / 8
Opposite side = s ; hypotenus = 8
Tan y = opposite / Adjacent
Tan y = s / t
Adjacent side = t
Then ;
Cos y = Adjacent / hypotenus
Hence,
Cos y = t / 8