Rich G. answered 05/07/20
Experienced Pre-Calculus/Trigonometry Tutor
For an equilateral triangle all the angles equal 60° and the sides are equal length.
The problem says the height is 10 cm. If you bisected each triangle you would get two 30°-60°-90° triangles, with the 10 cm height adjacent to the 30° angle (I wish I could draw a sketch on here)
If we use tangent, we can find the length opposite of the 30°
tan 30 = x/10
.5774 = x/10
5.774 = x
Since x = 1/2 the length of the side of the equilateral triangle, if we double x we will find the length of each side of the equilateral triangle
2x = 11.55
Now we know that each side of the equilateral triangles is 11.55. If we multiply this by 6, we find the perimeter of the regular hexagon
11.55 * 6 = 69.28
Hope that helps, feel free to ask any follow up questions