# Integration bounds in a continuous charge distribution of a semicircle

Why are the integration bounds from -pi/2 to pi/2 and not 0 to pi?

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## Answers and Replies

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gneill
Mentor
Why are the integration bounds from -pi/2 to pi/2 and not 0 to pi?
Because the angle is with respect to the positive y-axis.

what's the proof? I can't understand why this is the case

Thank you

gneill
Mentor
what's the proof? I can't understand why this is the case

Thank you
Look at the diagram. Note where the angle θ is. If θ was 2π, where would that put the radius vector?