



 
Hi Bruce. I always start geometry problems with a diagram, adding variables and extra lines as I go: There are two key ideas here: 1. The relationship between the radius, the arc length and the central angle (when measured in radians) is: a = rθ. 2. The top triangle is a right triangle, so knowing r and θ permits you to find x using cosine. Since h = r  x, that's the last piece of the puzzle. Thus,
Just remember to use radians rather than degrees for the angle in the cosine. Alternatively, convert to degrees by multiplying a/r by π/180. Cheers,  


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