Answer:
x ≈ 12.9
Step-by-step explanation:
In relation to the angle in this right triangle, the sides marked are the adjacent side and the hypotenuse. The relevant trig relation is ...
Cos = Adjacent/Hypotenuse
cos(72°) = 4/x
Multiplying by x/cos(72°), we have ...
x = 4/cos(72°)
x ≈ 12.9
