The three 500 g masses in the daigram are connected by massless, rigid rods to form a triangle. What is the triangle's rotational energy (in J) if it rotates at 1.50 rev/s about an axis through the center?

Question

(Diagram shows equilateral triangle with 500g masses at each point, the distance from point to point is 40cm and it has three 60deg angles [equilateral])

I keep getting the same thing and it's wrong

Answer 1

energy= 1/2 I w^2

I= 3*mx^2 where cos30=x/.2meter

m= .5kg
w=1.50*2PI rad/sec

Answer 2

I do not understand the part in which you solve for x. Is it supposed to be the cos of 60 equals x divided by .2?