**1. The problem statement, all variables and given/known data**
A uniform 5.0-kg ladder is leaning against a frictionless vertical wall, with which it makes a 15* angle. The coefficient of

friction between ladder and ground is 0.26. Can a 65-kg person climb to the top of the ladder without it slipping? If not, how high can the person climb? If so, how massive a person would make the ladder slip?

**2. Relevant equations**
**3. The attempt at a solution**
So, I choose the end of ladder that is touching the floor to be the axis. Now I want to find the sum of the torques, then set them equal to zero. What I don't quite get in the equation is the sin(90-15) in the first term in the following equation my professor gave me:

sin(90-15)? Technically, it should be the angle between the r and F....but this doesn't make sense to me....or perhaps 15* is meant to be the other angle in the triangle?

If anyone can help, it would be greatly appreciated. Thank you!