Mechanics - Statics

For part b

Resolve horizontally (right)

−F cos 42◦ + Rsin 42◦ = 0

I understand the Rsin42 but don't see how they get the Fcos42 can't see where they put the angle in.

I would usually do this by resolving perpendicular and parallel to the slope, FWIW. But, going by your method:



The blue lines are horizontal and vertical (hence perpendicular to one another). I get the 48 degree angle since the horizontal blue line is perpendicular to the vertical downwards black line, so the angle is $90 - 42$. Then the angle between the the perpendicular red line and parallel up-the-slope black line is again 90 degrees, so the angle between the blue and the up-the-slope black is $90-48 = 42$ again.

Thanks

Yeah that is how I did it but in the question it said "by resolving horizontally and vertically, or otherwise". So I thought this way may be easier but it isn't, compared to the standard way.