What you can do for this case is to use the following trigonometric definition.
sine (x) = a / h
Where,
a: side of the triangle.
h: hypotenuse.
Clearing to:
a = sin (x) * h
Substituting:
a = sine (45) * (4)
a = (root (2) / 2) * (4)
a = 2raiz (2) cm
Answer:
2raiz (2) cm (option 2)
