Answer:
x = 8
Step-by-step explanation:
If a triangle is equilateral, each vertex has an angle that is equal to 60 degrees
As we can see, we have two sets of similar right triangles
The value x faces the right angle and that makes it the hypotenuse
Also, the side measure 4 is the adjacent side to the angle 60
The trigonometric identity that relates the hypotenuse and the adjacent is the cosine
it is the ratio of the adjacent to the hypotenuse
Mathematically;
cos 60 = 4/x
x = 4/cos 60
x = 8
