If tan x = 4/5 and 0 < x < π/2, then sin x =

Tan x = sin x / cos x

you alright have sin x top number 4 now all you have to do is perform the pythagorean theorem of a^2+b^2=c^2

here a is 4, b is 5 and you need to find c

so

4^2+5^=c^2

16+25=c^2

41=c^2

now you square root the the

√ (41) = c

answer is 4 / √ (41) or depending on your teacher 4√ (41) / 41. But that is if they don't like √ on the bottom of functions

Wolfram Mathematica gave this answer ...