You can put this solution on YOUR website! About how far does the tip of a 1.8m pendulum rise as it swing 24* (degree) to one side?
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The arc is 1.8*2*pi*(24/360) =~ 0.754 meters
The distance from the center line = 1.8*tan(24) =~ 0.732 meters
The vertical distance from the bottom center = 1.8 - 1.8*cos(24) =~ 0.1556 meters
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Pendulum swing is usually limited to ~8 degrees each side of center.