Hello!
This is an equilateral triangle. In this triangle, the angles are congruent, respectively, the sides. Here, the mediator corresponds to the bisector, the median. So this line will form two right triangles.
Th 30-60-90
I used the 30-60-90 theorem, which says that the opposing the angle of 30 degrees has the length equal to half the hypotenuse.
Th Pitagora's
Which states that the sum of the squares of the legs of a right triangle is equal to the square of the hypotenuse.
Good luck:)