Question 302858
Let's the angle be x

sin x = {{{ 4/5 }}}

This shows that the side opposite angle x is 4 and the longest side of the triangle is 5. 

This means the missing length should be 3. 
Using Pythagoras Theorem, 5^2 = (4^2 + ?^2) 
25 = 16 + ?^2
? = sqrt( 25 - 16)
? = sqrt (9)
? = 3 ( hence shown )

tan x = {{{4/3)}}}

cos x = {{{(3/5)}}}