Hi there!
We can use right triangle trigonometry to solve.
We are given the angle's adjacent side and are trying to solve for the hypotenuse, so:
Use cosine: cos Ф = A / H
Thus:
cos 30° = 17 / H
Simplify:
0.866 = 17 / H
Isolate for H:
H · 0.866 = 17
H = 17 / 0.866
H = 19.63 ≈ 19.6