Given sin t= 2/5 and cos t> 0, find cos t

Sin t = 2/5
sin (angle t) = 2(opposite)/5(hypotenuse)

cos t > 0
meaning cos t is not a negative integer.

and

cos (angle t) = (adjacent)/5(hypotenuse)

let’s call the unknown adjacent (a)

therefore,
cos t = a/5

sin t = 2/5

Adjacent = ?
t = ?
hypotenuse = 5
opposite = 2

Applying the pythagoras theorem,
adjacent^2 + opposite^2 = hypotenuse^2

Therefore, substitution will be done:
a^2 + 2^2 = 5^2
a^2 + 4 = 25
a^2 = 21
a = 4.58 (3s.f.)

Hence,
cos t = adjacent/hypotenuse
Would be:
cos t = 4.58/5

Therefore the answer is 4.58/5.

Hope this helps and have a good day ahead! :D