Ablock is held at rest against a wall by a force of magnitude f exerted at an angle theta from the horizontal, as shown in the figure above. let fg be the gravitational force exerted by earth on the block, fn be the normal force exerted by the wall on the block, an ff be the frictional force exerted by the wall on the brick. which of the following statements about the magnitude of the forces on the block must be true? select two answers.
a.) f = fg / sin(theta)
b.) fcos(theta) = fn
c.) fsin(theta) = fg + or - ff
d.) f = fg + fn + or - ff