I have a question that i am struggling to come to terms with. I know how to get the answer but i am not 100% sure why what i am doing works. The question : A smooth plane is inclined at X degrees to the horizontal. A block of mass 5KG is held at rest on the plane by a horizontal force of magnitude 168N. Find : Angle X The force on Normal on the block. Ok, so far i have this. i seperated the horizontal force of 168N into a force horizontal and a force parralel to the plane. Horizontal : 168CosX = 5gsinX parallel : N = mgcosX + 168sin X Now somehow, and this is the part i do not understand 100% you get to the equation 5gcosX=168cosX sinX/cosX=168/5g tanX=168/5g so then X is the tan^-1 of (168/5g). and then you put it back in the parallel equation to find N, the normal. Can someone explain to me how you come about reaching these equations : 5gcosX=168cosX sinX/cosX=168/5g tanX=168/5g thank you.