- #1

- 158

- 10

- Homework Statement
- Why angle direction is perpendicular?

- Relevant Equations
- vector

The unit vector r roof points in the direction of

increasing r with phi fixed; phi roof points in the direction of increasing phi

with r fixed. Unlike x roof, the vectors r roof and phi roof change as the position

vector r moves.

What I was thinking of the image is

Although, I was thinking why phi roof is perpendicular.