# How to calculate the coordinates of the middle point of a given arc? [duplicate]

Possible Duplicate:
How to calculate the coordinates of the middle point of a given arc?

I am trying to calculate the green sides of this triangle:

I know/have:

• the arc length,
• the arch base,
• and the h (distance from the red dot to the center of the circle)
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 You only need to know the lengths or the exact position? Because two points (and the arclength) doesn't define the circle unambiguously. – WebMonster Dec 15 '11 at 11:57