In a 30°-60°-90° triangle the hypotenuse (c) is twice the length of the shorter side (a):
So a = 12/2 = 6
The longer side (b) is equal to the shorter side multiplied by √3:
So b = 6√3
The three side lengths are:
a = 6
b = 6√3
c = 12
The perimeter is the sum of the 3 sides:
Perimeter = 6 + 6√3 + 12 = 18 + 6√3
The answer is D.
