Explanation:
I find it easiest to remember one or two facts and use those to figure others when needed. The primary fact I remember is
π radians = 180°
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From this, you can determine ...
360° = 2π radians
90° = π/2 radians
60° = π/3 radians
45° = π/4 radians
30° = π/6 radians
The other angles on your chart are multiples of 30° or 45°, so will be corresponding multiples of π/6 or π/4 radians, respectively.
