This is a rod attached to a wall by a light inextensible string:
And here is a diagram showing the forces acting:
I want to find the normal reaction $R$ between the rod and wall using moments about $C$.
A moment is the product of the force times the perpendicular distance from the pivot. So the moment created by $R$ is $R * 2$. Though I cannot find any other perpendicular forces acting in the opposite way to use the principle of moments.
The mark scheme for this problem says that $R(2) = 3g\cos30$, but $3g$ acts parallel to the direction that we measured $R$ from. So I do not see how we can even include $3g$ because resolving it through $\cos30$ makes it perpendicular to the rod, but not the direction we measured the distance for $R$. Can someone explain this to me?