Hi, could anyone help me with understanding this please?
"A crate of mass 30kg is at rest on a slope which is at 18 degrees to the horizontal. Find the frictional force."
The frictional force = 30gcos(72 degrees)
I don't understand this because cos(72 degrees)= adjacent/hypotenuse, so cos(72 degrees)=30g/frictional force
which means that the frictional force=30g/cos(72 degrees)
Thanks in advance