Which relationship gives the critical angle θc at which the block begins to slide down the ramp?
a) sin θc = (Coefficient of friction) / (Coefficient of static friction)
b) tan θc = (Coefficient of friction) / (Coefficient of static friction)
c) cos θc = (Coefficient of friction) / (Coefficient of static friction)
d) cot θc = (Coefficient of friction) / (Coefficient of static friction)