Answer:
3.76 units
Explanation:
We want to use trigonometry to solve this - specifically, the trigonometric function sine, which is opposite divided by hypotenuse.
Here, the opposite side is AC, which is what we want to find, while the hypotenuse is AB, which is 4. The angle itself is angle ABC, which is 70 degrees. Now, write:
sin(70) = opposite / hypotenuse = AC / 4
Multiply both sides by 4:
AC = 4 * sin(70) ≈ 3.76 units