Question

Find the cosine of angle Y

Answer 1

Cosine = adjacent ÷ hypotenuse 

So the cosine of ∠y would equal 64/80 
64 being the adjacent side 
And 80 being the hypotenuse

cos(y) = 64/80 = 4/5

The answer would be 4/5 or 80°

Answer 2

The cosine of angle y would be equal to the length of the adjacent side over the length of the hypotenuse. 

cos(y) = $\frac{64}{80}$ = $\frac{4}{5}$