First we need to create a triangle. Since it doesn't matter what shape the triangle is, just put three points somewhere on the screen.
Use the arrow tool and select two points. Under the construct menu, construct a segment (ctrl-l). Do this for all three sides of the triangle. It is possible to construct all three sides at the same time by selecting all three points and constructing segments.
Depending on which triangle centre you want to construct, you might need to create midpoints. To do so, select a single line and go to the construct menu -> midpoint (ctrl-m).
Centroid |
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Circumcentre |
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Orthocentre |
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