A pipe comes diagonally down the south wall of a building, making an angle for 45 degrees with the horizontal. Coming into a corner, the pipe turns and continues diagonally down a west facing wall, still making an angle of 45 degrees with the horizontal. What is the angle between the south wall and west wall sections of the pipe?
Dot products invariance under the rotation of a coordinate system
The Attempt at a Solution
My main problem is actually visualizing the question. I feel as if it just an application of the parallelogram rule for addition of vectors and then finding the angle. Arfken says the solution is 120 degrees.