If two angles of a triangle are 30° each and the longest side is 10cm. Calculate the length of each of the other sides.

A.
5cm 
B.
4cm 
C.
3√3 cm 
D.
(frac{10sqrt{3}}{3})cm
Correct Answer: Option D
Explanation
Let each of the unknown side be x.
(10^{2} = x^{2} + x^{2} – 2(x)(x) cos 120)
(100 = 2x^{2} – 2x^{2} cos 120)
(100 = 2x^{2} + x^{2} = 3x^{2})
x = (sqrt{frac{100}{3}})
= (frac{10}{sqrt{3}}) x (frac{sqrt{3}}{sqrt{3}})
x = (frac{10sqrt{3}}{3})cm